Nose heavy? What's that????
A bit of ballast in the tail will be no big deal. Have you used that power system on your models before?
If not, you're in for a pleasant surprize.
It'll have plenty of power and at your estimated weight I would think it'll cruise at just a bit over half throttle.
Good idea layering the decals. I'll store that one away in the old noggin for future use.
Now, if only I don't forget where I put it!
The starship, I experimented with your method on some scrap foam first.
The glue stick just didn't seem to work well here. While it did adhere the tissue ok at first, after sitting in the hot humid garage for a few hours the glue starts to turn purple again and the tissue wrinkled/lifted. I could iron it back down and it would be nice and smooth again, for a while.
I tried a few different adhesives and found 3M spray to work the best. Same tecniquique, spray, allow to dry and attach the tissue with heat. Looked good for a week or two, then it started to wrinkle too.
Steam just might be the answer, it will shrink the tissue a bit.