I can't quite see what the problem is with the exhaust, it should run just above the stitch line on the fabric. You did a good job with the repair of the damaged decal, what I usually do in a case like this is to cut a piece of white decal to the correct size and shape and apply it over the damaged section. After I apply my decals and giving them time to dry I always spray them with a clear coat, this protects the decals and gives the correct sheen, either a satin ot matt clear. You are doing a great job with your build, this has been a fantastic learning curve for you and you will find your next build to be a lot easier. Keep up the good work and I look forward to seeing the top wing mounted.
Des.