Is it difficult to install new pads under a 26 Roadster top?
It's not "difficult", but it's not a slam dunk either. You have to take the top loose, front and back, and on each side, at least a few inches beyond the pad. Sometimes the pad is put on and ends up under the rear curtain, so that may have to be peeled back also.
The problems come if the top is very tight or shrunk. On a new top, you have extra material overhanging front and rear bows to pull and then tack. Taking the old top partially off (I'd leave the middle portion front and rear still attached to bows) and getting it back in place takes some patience, particularly if the top has "shrunk" to fit what may be thinner pads.
If you take the time to do this, go back with a good padding inside the pads, not foam. Assume the reason you want to do this is the pads have deteriorated? I've found that 40 ounce jute wrapped in a thin layer of cotton batting makes a great padding material.
I've been asked to replace pads on very old, or original, tops, and refuse to do so. If top material is brittle at all, you'll never get it back together properly, and will probably do more damage than good.
David, thank you. That's great information as I wasn't sure what I was getting myself into. This puts my my mind at ease. The top is in fairly good condition but it hadn't been down in a long time. The pads have deteriorated enough that when I put the top down to load the car on the trailer, they tore on the drivers side. I purchased what look to be some quality pads (no foam) but like I said above, I wasn't sure what I was getting myself into. The top seems tight so it may have shrunk a bit but the material is still very pliable.
Thanks again for the advice.