Your just asking to oval or crack a stock sleeve unless the stock sleeves were pinned. I have a good builder and topspeed is no slouch in tuning. For me personally I just wouldn't push my luck and that's what I've heard from several other builders and tuners. I want my expensive build to last and it's not worth pushing the stock sleeves for a few extra psi. You were talking about running 28-30 psi that is just a lot for a stock sleeve if your looking for reliability. Not saying your builder or tuner isn't good or that your motor can't handle it but the question is for how long can it handle it.