Good question. I like to make some pretty careful marks on the firewall, for centering and offsetting the engine mount. At the time, it's just one more mark to put a mark on the top of the firewall, an eighth of an inch to the side of the centerline. A piece of string taped over that mark and run back over the fuselage gives you a good eyeball reference for aligning the vertical stab, or the slot it goes in.

Before the fin, though, I'll get the wing aligned, again with string and reference points. Then the stabs go on, with the wing providing a place to block up the fuselage upright. With the table, string, and a big triangle, you can eyeball everything into place.

Good luck,
Dave Olson