A couple years ago I settled on a MP size and configuration that fit me well. A couple months ago I started messing around with throat size for two reasons. I was occasionally getting an unclean buzz on High G, and sometimes it felt like the mouthpiece was swallowing my face. So I went from a #25 throat to a #27 throat. It helped on both issues after a couple weeks. It also focused my sound a little and I liked that. The Wild thing plays with a huge, broad sound anyway, so focusing it a little is fine to do.
I then got to wondering if a smaller size might be in order. I am one of those guys who has responded very well on every step smaller I made. By that I mean my response, flexibility, and control improved without lessening the quality of my sound. So I had Dr Dave make me a MP top that was .010" smaller than my current with a #27 throat. That's when things became interesting.
I am at a crossroads in my playing. Actually, I have just started down one fork. During gigs, I am pretty strong to a High G. I can sometimes get a High A. In practice I can usually get DHC. However, I just don't own those notes above High G--yet. The path I was on with the #25 throat was to force out those notes above High G by just using more air. The problem with that approach is it kills endurance and isn't the real solution for owning those notes. The smaller throat will shut me off if I overblow.
The end result of all this is with my current size, the #25 throat spreads the sound a little and makes it easier to force out notes above High G. The #27 throat focuses my sound a little and requires me to use proper technique to play those notes above High G. In fact, for every note except those above High G I like the #27 throat better. Of course, when I back off the force, The #27 throat speaks just fine above High G.
The one other thing I am going to try is my smaller top drilled out to a #25 throat. The smaller cup with it's current #27 throat does seem a little small in that it will shut me off more quickly than my normal size with the same throat. Perhaps with the #25 throat the smaller piece will balance better for me. My tone is fine on it. If it doesn't work, maybe it will for the picc. I DO like a bigger throat on the picc since it is a tight little beastie. If it doesn't improve anything at all--which is the likely outcome, it does answer the question as to what is the optimum MP size for me.
Whenever I get to experimenting with stuff, whether it is throat or backbore or gap or tuning slide, I will find a slightly different combo that I think makes it easier to play above High G. The funny thing is the next day, that easiness is gone and I am back to my original set up. In messing around with this I've finally discovered that the real secret to finding that easier set up is to take a break for a few minutes. After a few minutes break, whatever combo I use works better than when I was just muscling through stuff.
The real answer for me is to continue down the path of finesse for the extreme upper range, with whatever MP and throat I use. I need to rest more when I practice, continue with the Reinhardt stuff Chris Labarbera gave me, and keep using my PETE--just started with the PETE.
One last thought. I typically use the tightest slide (#2) with my Wild Thing. I have found some consistent improvement above High G with the #3 slide, which is just a little more open. However, my tuning slide has to come out another 1/4" with the #3, and my intonation seems to be more consistent with the #2. I think my endurance might be a little better as well with the #2. I had been using the #3 for a while, but last summer while playing most of the lead for Fiddler on the Roof I changed back to the #2 and everything seemed to get better. My theory is the more open slide lets me force things a little more, which like with the MP throats, works great for a little while but is bad for the long term.
One this all this messing around with equipment has shown me is that the next step in range and endurance for me isn't going to come with an equipment tweak. I need a little more embouchure strength, but I need a big change in how I practice and play--that being more finesse, less force, more rest during practice.