I would have to disagree. Static pressure cools nothing. CFM in fact has the only meaning in the world of thermodynamics 0 cfm = 0 cooling..... static pressure comes into play only if there is a lot of resistance, that isn't able to be overcome by static pressure provided by the fan, the cfm doesn't get there to do the cooling. BUT, It's not what SP the fan provides on it's own, that;s meaningless.... it's the relationship or difference between what SP the fan can provide and what resistance is in its way. The same rules don't apply when the same conditions don't apply. We can't apply 60mm and 80mm med - high rad rules to a low fpi 30mm rad. To make an analogy...Is horsepower the only thing that matters in racing ? It's not about horsepower, it's about horsepower to weight ratio. We don't need the big HP here because we don't have a lot of weight.
On your typical 60 mm pr thicker rads I'd be a bit concerned.... ST30, much less so .... it's designed as a low fpi low resistance radiator and the usefulness of the fan in this situation can only be measured
in that context. Static pressure is needed only in proportion to the resistance to be overcome. Looking at martin's charts, we see that the half as thick ST30 performs better than it’s big brother the UT60 at low speeds .... how can that possibly be ? At 1000 rpm, the fans in the test don't produce much static pressure and we see that the ST30 does better for the simple reason that it presents much less static pressure and the low speed fan is able to push more air thru the 30mm rad than it can with the 60mm one. That I think is the point getting lost here. We are talking a very low resistance rad so we don't need a high SP fan. We also don't know what the goals here are regarding noise..... for example, I don't wanna run over 1250 rpm so I don't have noise issues and at low rpm's, SP is much less of an issue.
Now we have a test site confirmng that the "Even though the fans are 10mm thinner than the regular models they performed really, really well offering very nice and stable airflow and a decent static pressure level
."....It was not tested as a case fan but it's performance was measured pushing air thru the much more tightly spaced fins of an large air cooler and it kicked some serious butt. Will it beat a typhoon, I doubt it and can't say as it wasn't in the test....But it did beat a slew of Noctuas, BitFenix, Scythe, Enermax and Noiseblockers. I'm not saying its king.... but I think it did fairly well. And these results are echoed by newegg users who have it pushing air thru tightly spaced fins
Again since static pressure is also required to push air thru the big air coolers with their tightly spaced fins and we see that several fans finished ahead of the typhoon in silentpcreviews testing. The typhoon is a great fan but there are other great fans out there like the NBs.
Now if changing the case is an option, if he has the room, the budget or inclination, I'd say yes, try and find something ya like as much that doesn't have this limitation. But if this is going to be "the case" and he as an XT45 in his build plan and is considering an ST30 for extra cooling, ...... yes, if he had room for a single 25mm fan, I'd say by all means, grab something with more oomph .... but since that is not an option, I dare say his system will run cooler with the 15mm fans than it would with no fans at all. And with something which provides as little resistance as the ST30, I see no reason why a fan which performed as well as it did pushing air thru that big ass cooler would do much worse such a thin, low fpi radiator.