Dave,
I'm not an expert on fiberglass doors, but here are my observations and opinions from reading and talking on the subject over the years:
I am under the impression that such doors should not be cut or even planed. The doors are not one giant slab of fiberglass. I believe that they are somewhat analogous to the interior slab doors which many of us have encountered: there is an internal wooden structure made up of interlinked wooden pieces. I would guess that the entry door would have some foam insulation between the wooden members, and then a skin of fiberglass is over the entire framework.
I suppose that you are limited to a custom door. You could contact one or two manufacturers and quiz their technical department about the wisdom of attempting to shorten one of their fiberglass doors.
If I may ask, why do you need to strip and refinish your current wooden door every few years? I investigated a steel or fiberglass replacement entry door because of a similar problem with our wooden door. I made a few changes and the longevity of the wooden door finish has improved considerably:
1) I replaced our full-view storm door with a new one which has a built-in screen which rolls down from a hidden mechanism. In the summer we can create a small (2"-3") screened opening at the top of the storm door to help vent "greenhouse" heat. I believe the new storm door was purchased from Home Depot. If not, then it was bought at Lowes.
2) I switched the door color from black to very bright white. I actually used Kilz2 as a finish coat. It reflects sunlight extremely well and it has proven to be quite attractive.
This has helped us in our particular situation very well. The door was getting baked by the sun every day and the dark color plus the full glass storm door were creating extremely high temps. Resin would actually bubble out from the wood and had to be sanded down every
2 years or so. Not any more.
Good luck, Gideon
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