Well if it raises compression then generally you can expect 5% overall power gain per point increase of compression. figure the Beta II engine makes 120whp @ 10:1, compression of 11:1 could potentially yeild 126whp.
The best way to get power from the 2.0 Beta II is to boost it. A few years ago finding a boosted Beta was not very common but now they are all over the place so the knowledge is readily available if you require help. I dont know of anyone who has sucessfully built a high compression motor.