I had an idea to use old JRI as the basis of a completely different map, only to save the original peninsula road. I have a cache of 0.20.2.0, but it does not seem to contain the complete level; only some art was saved. How and where would I go about finding those old files? Not sure where else to ask.
You could roll back to 0.14 using the steam betas tab if you're using the steam version. 0.14's JRI is essentially the same as 0.20's, minus a few bugfixes.