All lot of builders put this off until the final finish phase of the project. I decided that I was going to complete each component in its entirety (short of paint). That way there is not allot of fine detail work left to bog down the final phase.
The fiberglass parts provided are pretty rough. They are laid up with polyester resin vs. epoxy. This means they will shrink and change shape for a long time before the U.V rays finally harden the modulus in the resin. I figured the sooner I get them firmly mounted in their final position, the longer they will have to post-cure in that position and take the final shape.
Fitting the part was time consuming but worth it. Tighter the fit, the less filler required, the less weight added. I fine-tuned the joggle with a file and sanding block until it fit with a minimal gap.