Starting with modding engines is most of the time trial and error. Ofcource messuring other engines is giving a lot of information but copying timings from one to another brand or even to a same kind of engine does not mean it will always run the same due tolerances and used materials.

Once I did go to far with an exhaust of an experimental because the sleeve mounted in another crankcase was placed a little bit higher but the engine did run fine. Later with the Flash tuned special my fault was confirmed that it can be even made higher.

Finally after a lot of experiments on old engines you will know what works.