Hi Terri!
Beautiful little project, a rare bird in our field.
About cowling, Karaya produced a resin version of your engine:
http://www.karaya.pl/en/karaya/11/siemens-halske-sh-iii-engine-kare4807.html?ref=%2Fen%2Fkaraya%2F11%2F2%2F1%2Fitems.htmlBut, of course, you don't know if it fits well in your cowling if you don't have in your hands.
Did you try if metal cowling fits well to fuselage?
You may try to obtain a copy made with transparent acetate, using metal cowling as master.
If you have a piece of transparent acetate, put it on a candle. When you see "wave moving" in it, press it with a fast move on metal cowling, fixed on a stick before.
The transparent acetate will adhere to master. After few seconds, you may remove the printed transparent cowling, clean the part cutting away acetate excesses.
Hope my explanation is clear!
Hope useful too!
Roberto