Sounds like alot of extra work for what may not work as well. I would hope somethought went into the new spring design and so far they seem right on. Also those parts are about the the same cost as they currently sell the Adult springs for 24.95 shipped.
Although I considered just adding a large nylon spacer for preload that would probably be fairly inexpensive if they are available at a LHS, they may be custom made also.
Probably what would help more than a stiffer spring is adding dampers, now that sounds expensive to keep the original look and I wonder how many are Riders as compared to Collectors. The originals did feel a little dumpy if that works. But I also plan to lose 30 pounds, should help on the hills