Late test report: both programs are quite fine. restunts.exe is noticeably slower than the original game under DOSBox, but that was unavoidable of course. Other than that, mostly everything seems ok. The error on the track editor says something about being unable to handle sdtedit. One related observation is that I tried at first launching both versions from my "sandbox" Stunts installation, which has an edited sdmain.vsh (the menu signs being translated to Portuguese). Strangely enough, it crashed with the same complaint, only mentioning sdmain instead of sdtedit...
By the way, is there any way to choose which shape will be loaded by the restunts-alt?