RE: Just a little respect for the SPA...
as many have stated, if you believe that all the planes should be per plan, original style engines and such, that's great. Build your plane the way you want to, power it with what you see as proper and bring it out and fly and have a good time. You will find out it's the carpenter not his tools. If you are good, you will smoke everybody with your original plane, believe me. If it's "not about that", than where is the argument? Everybody is free to build a plane exactly per the plan. You will find a modern 61 with muffler about 6-8oz heavier then a period correct 2 stroke, so you'll have a lump of lead on the tail. Done deal.