One trick that works to make sure the fuselage is straight is to use a laser level that can provide a vertical reference line. This can be projected lined up on the nose and tail, then marks placed on the fuselage where it crosses bulkheads. This will let you see how far something needs to move to make everything straight. You can line it up on the end of the crank and the glow plug to check to see how the engine is set. If you sketch out the engine mounting, you can use them as reference and set the right thrust accurately with the laser line. The one I use is self leveling and projects both horizontal and vertical lines and makes assembling a model much easier.

Hogflyer