but I believe you're overthinking it, Larry. Once clamped up, including some aluminum strap "hinges" at the top edge, I found the door would migrate slowly downward in the doorway opening as I trimmed the edges progressively so the door would drop down flush with the canopy. This mitigated my careful pre-positioning efforts and left me with less (but still plenty) of lower door flange when complete.
Center it the best you can, cleco in place with some aluminum plates across the gaps, and sand it into a good progressive fit. There's almost nothing you could screw up in this process that couldn't be fixed with fiberglass.
Hop-Along Aerodrome (12VA)
RV-6A - N30YD - flying since '98
RV-10 - N130YD reserved - under construction
donating monthly to the VAF - thanks, Doug