Yes, I'm going to be running an on-center block with a sleeve. I'm shooting for 1000 hp right now, but I think my motor is good for ~1500 hp and the sleeve doesn't bother me one bit. You might be suprised how many stage blocks have sleeves. You probably haven't heard of many because it's not something people announce regularly because if done right it's not a concern.
Read the description of both of these motors that were for sale.
http://www.turbobuick.com/forums/threads/any-interest-in-going-fast-8-sec-street-car.317585/
These were some of the fastest iron block, production head motors around. Both made big power and one of them is probably about to be the highest hp production head motor. Both shortblocks have sleeves.
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Bringing this thread back since I ran across it. I now own that motor. The sleeve cracked at 800 hp. It also dropped twice before it cracked. My advice to anyone is stay away from anything sleeved.