No sacrifice. If you have both machines, and (critically) want to run them both at the same time, the 520 will run with the CC board in it. It'll just be big and slow while the CC is small and fast. You can always reverse the process and have big and fast when you want to.
Overclocking a 520 to 33MHz wouldn't make it a 575 (an '040 Mac), it would make it a 550. Still an '030 machine, but silly fast.
Uni - have you got a 128MB SIMM to work in these? If so, an overclocked 520 or 550 with 132MB RAM would be about the coolest pre-Quadra Mac (especially in a 640x480 modded CC). Even at the nominal maximum 36MB RAM, it's a pretty sweet machine.
Overclocking a 520 to 33MHz wouldn't make it a 575 (an '040 Mac), it would make it a 550. Still an '030 machine, but silly fast.
Uni - have you got a 128MB SIMM to work in these? If so, an overclocked 520 or 550 with 132MB RAM would be about the coolest pre-Quadra Mac (especially in a 640x480 modded CC). Even at the nominal maximum 36MB RAM, it's a pretty sweet machine.