By "My version" I assume it is a splitter you made,or possibly one of those Harbor freight ones.
I have a Split Fire 3465 that has an 11 GPM pump and it has a Honda 6.5 Hp engine. So far I have not found nothing this splitter will not split(I am sure there is a round out there some where to prove me wrong). This splitter is compared to a typical 16 GPM/22GPM splitter. That is because it has a little less power on the return stroke. This will split using a four way wedge or back to a 2 way wedge. I can split a long time with that 6.5 Honda,I love this splitter. Turbo 885 saw it run Saturday,ma-be he will comment on it. The biggest splitter they make is a 4490. This has a 16GPM pump that is the same as a typical 24GPM/32GPM pump. This splitter only uses a 9 HP Honda. I believe the secret is in the Wedge design and the small point the round is placed against,so you are only using pressure on a small part of the log,compared to pushing the whole round. If your design is close to the actual Split Fire I would assume you could get by with a 9 or 10 HP engine.