The very best pipe i have ever used was a meershaum pipe, made from some middle eastern marine something or other, very light and heat resistant.
The thing that made that pipe so nice other than being so light that i could forget it was dangling out of my mouth, was the size of the opening all the way through the pipe, it was about 1.5mm. The result of htis is that one requires a lot more suction to get it to come through, but the smoke for some reason is cooler, and it never occurred to me until reading the idea about reducing the air flow to effectively lower the air pressure and reduce the boiling point.
This is probably not so relevant to the smoking of methamphetamine HCl, since it requires a certain amount of heat to dissociate and liberate the meth base vapour (eeuuww, just realised that smoking meth means also inhaling a small amount of tooth destroying vapourised hydrochloric acid), perhaps more of more interest to those interested in ingesting freebases via a glass-dick type of pipe.
The one thing i learned when i first got my basepipe was that you had to suck very slowly, otherwise you would end up with droplets of hot freebase etc in one's mouth.
It never quite occurred to me that i might be able to perhaps constrain the air intake of the pipe so as to increase the amount of sucking required as i have intuitively grasped that reducing the rate of air flow makes the smoke cooler, even if droplets don't get into your mouth in the vapour stream, the problem of pyrolysis raises its head, and this is a greater problem in the case of impure mixtures which may contain quite high boiling compounds such as waxes and fats and oils and tannins etc.
Certainly this would reduce the temperature required to the temperature of the dissociation of the salt, which obviously would help a lot in reducing pyrolysis.