Well the simple way would be to halve the SM blocks, so each one is made up of 16 cores drop one cluster and you 240 in total.
The big question for me is what's the ROP count going to be? it's the combination of lower ROP and memory band width that which seems to make the big impact of the 5770 esp with any effect heavy graphics, just pushing filled polys it's not far behind the 5850.
Hopefully this is going to be a better priced card, however with the cost & production issues of the gf100 chips I doubt we'll see these cards that aggressively priced.
As much as I'd like this to be the new 8800gt I doubt it will be.
180TDP

strapping a TRUE to a graphics card is looking more and more like a good idea.