The gemara[3] states that the length of a single teki’ah blast is like that of a set of teru’ah. The gemara does not actually say that one is longer than the other, but it is obviously impossible for them to be of precisely the same length. Apparently, the teru’ah’s length is used as an objective point of reference for the teki’ah; the teki’ah must be at least as long as a normal set of teru’ah. This may be one of the reasons that there are no opinions found in the Tur, Beit Yosef, Shulchan Aruch, or classical commentaries that say that it matters whether the teki’ah or the teru’ah is the longer one during a given series. What matters is only that each one independently is as long as it is supposed to be. The length of the teki’ah is therefore unaffected by one making a longer teru’ah set than he needed to. We will note a few of many possible proofs to this thesis.
Poskim use an individual teru’ah blast (called a tarmut[4]) as the unit of reference for the lengths of the other blasts. For example, there is a machloket regarding whether each shever must be at least three tarmutin long or if, on the contrary, each shever must actually be no longer than three tarmutin.[5] In practice, we accept the opinion that the teki’ah of a teru’ah series must be at least nine tarmutin long, and the teki’ah of a shevarim-teru’ah series must be at least eighteen or so, paralleling the eighteen tarmutin of the shevarim-teru’ah. Thus, the length of the teki’ah must each time be at least as long as the required length of the middle section of that particular series.[6] But according to the approach your makri suggested, these lengths are of very limited relevance, as they need to be increased if the middle section is blown in a manner that is even only slightly longer than average.[7]
A major concern regarding the lengths of the shofar blasts is that blowing a longer than necessary shever, such that it reaches the minimum length of a teki’ah, would preclude its being defined as a shever and instead define it as a teki’ah. The poskim write that according to the opinion that a teru’ah set contains nine blasts (in contrast to the opinion that it contains only three), the length of the teki’ah must be at least nine tarmutin. Accordingly, an individual shever could be up to (but not including) nine tarmutin.[8] In theory, then, in a shevarim-teru’ah series – in which the teki’ah is at least eighteen tarmutin long, as noted above – each individual shever should be allowed to extend up to eighteen tarmutin.[9] But if one were to blow such lengthy shevarim and also posit that the middle section’s length cannot exceed that of the teki’ah, as your makri argues, then the teki’ah of a shevarim-teru’ah series could end up being upwards of sixty tarmutin – a length found only in some blowers’ teki’ah gedola.
Regarding the debate as to whether it is proper to blow more than three shevarim blasts in a set,[10] the Perisha says we avoid doing so because in a shevarim-teru’ah combination, one might run out of steam before getting to the end of the nine subsequent teru’ot blasts. In contrast, he notes, we are not concerned about extra teru’ot blasts,[11] as one can stop them whenever he gets tired. The Perisha does not say that we must be concerned that after an extra-long shevarim followed by a teru’ah or an extra-long teru’ah after a shevarim, the ba’al tokei’ah might not succeed in blowing a teki’ah that is as long as the shevarim and the teru’ah together. The reason is, once again, that the minimum length requirement of the teki’ah depends on the standard length requirement of the middle section; it is unaffected by the actual blowing of an unnecessarily long shevarim and/or teru’ah.
At least one contemporary posek, the Mo’adim U’Zemanim,[12] mentions a “practice of the stringent” to have the tekiot be as long as their adjacent middle section actually ends up being. He identifies one Rishon[13] (not cited by the Beit Yosef) and one Acharon[14] who share this opinion, but he concedes that this opinion is not found in the poskim.[15]
In general, we do not oppose unnecessary chumrot of fulfilling fringe opinions for those who desire to do so (perhaps especially on Rosh Hashana and regarding such a beloved and important mitzva as shofar blowing). The problem is that the way you describe your case, the tiny gain may cause greater problems than it is worth. As one who has served both in the capacity of a ba’al tokei’ah as well as that of a makri, I believe that a ba’al tokei’ah is much more reliable at counting teru’ah blasts than a makri is. If the makri tries to stop the ba’al tokei’ah after what he perceives as nine or ten blasts, whereas the ba’al tokei’ah is not yet confident that he has blown that many blasts, it is not unlikely that nine blasts indeed will not have actually been blown, and this could disqualify the set.[16] In fact, the Mo’adim U’Zemanim’s stringency assumes that the minhag is to blow longer teru’ot sets than necessary, and he therefore instructs lengthening the tekiot accordingly. He does not suggest being “stingy” with the teru’ot, certainly not to the point that a miscounting could cause there to be fewer than nine blasts.
While a ba’al tokei’ah should follow his makri’s stringencies, at least if he is the shul’s rabbi, in this case we suggest you show the makri the evidence we have presented. If he still does not change his opinion, you should, of course, follow whatever the rabbi says.