I'll have to try the 1/2A 6x4 as well. Whether it is the optimum or not dunno, but the 6.3x4 really performs on the .074.

My experience with EP-IC conversions and modernization of old kits is that an IC conversion generally comes out lighter, and when you put modern lightweight gear in a 30 year old design for 1/2A's, you can achieve similar AUW with a larger engine. My Baby Birdie as an example, with fully sheeted 12% wing modification seems it will achieve 24-25oz all done with a piped .15. Compare that to 22-23oz with a TD, NiCad pack, big servos etc. So for this thing, trading the weight of EP gear for the weight of a larger IC engine sounds like fun to me.

Mr Cox I think you prefer the results of lighter wing loadings with smaller engines, and that is a great direction to go. Some guys just like overpowering, the goals are slightly different but in the end they have just as much fun especially with these economical/cheap electric ARFs. A .15 on this would not be too radical, but it might not thermal.