Back when I smoked straights I recall that I kept the bit deeper in my mouth. I don't clinch my pipes, I let them ride in my mouth with my jaw set normally, the teeth do not touch when my mouth is at rest, this let the weight of the bowl drop down forcing the bit up against my back molars. With my bents, nearly all of my present collection, the bit rides a touch behind my canines on the front molar.
I find the P tips ride nicely against the front upper molar on either side of my mouth. Regular, fishtails, ride further back on the molars. The most comfortable straights for me were the Crosby's, for what that's worth.
It's a matter of balance for me and it's a reflex now as to where I feel the pipe is natural in my mouth.
Not sure I explained my technique very well, but feel is the key for me. There's little to no pressure exerted my the jaw and pipe feels natural in my mouth. When I talk with my pipe in my mouth there's is very little jaw movement sort of like the English.