We need to replace an ancient storm door (ugly gray metal) in our more ancient house [img]/forums/images/icons/grin.gif[/img] . I measured the opening at 3 places and the smallest measurements are:
78 7/16" x 30 3/8"
We stopped at the local box store (Lowes) and a standard size, 30" x 80", is too tall, so it looks like we have to order a custom door. [img]/forums/images/icons/frown.gif[/img]
Never heard of BetterBilt, but Pella is top-of-the-line in windows, and I'd assume that extends to their door line.
I've used aluminum storm doors that had adjustable bottom jambs that would fit a range of about 3 or 4" in height variations. You just hung the door to fit top and sides, then slide the bottom with the integral sweep down until it fit, and ran some self-tapping screws into it to hold it in place.
Not fancy, but effective.
For $277, I'd be wanting a solid wood door with fancy hardware and an insulated lite.
I like a wooden storm door. You can still get them if you go to a real lumber yard. They are pricey, but on an older house they look great and if kept up will last forever.
My house has 4 outside doors and I've had to replace the two aluminum storm doors which were both <20 years old. The other two doors are wood, at least 30+ years old and are still in good shape. Other than painting every few years and occasionally reglazing the storm window they should last forever.
If you don't mind doing some painting, get wood and you will have a door for life. Get one of the aluminum or plastic doors and in 15 - 20 years you'll be buying a new one. Another plus for wood is that they can be made to fit in any opening.
My Lowes carries Larson and Betterbilt... I have no experience with BB but the Larsons are great. If they can survive on the rentals, they can survive anything. Wood core and vinyl clad. Larson doors start at about $100 for plain white at the couple places I shop.