ORIGINAL: dbacque
After the pieces are cut you should get a fairly good fit. I use a long sanding bar to touch them up if needed, again watching carefully to keep the bar square to the sheet. Or you can make an edge sanding guide that will ensure a straight, square edge.
http://www.airfieldmodels.com/inform...ture/index.htm
Dave
I have used a set-up similar to this with good results and the same taping method that you are using with good success. Just needs patience and a little practice.