My experience is that Adobe CC extends time stretch by percentage to something in excess of 8 decimal points, unlike Reaper. With a simple audience file, a few (under 10 samples) might not be noticeable, but once you get into soundboard files, most people can tell the difference between 10 samples. Adobe Audition 3.0 is, I have been told, more accurate, and can improve time synching by 3-4 samples per synch point, but Hoserarma is the expert in this matter. I use Adobe CC for placing the markers and stretching. Mr. Hose uses Adobe CC for placing markers and then uses Adobe 3.0 for the stretching.
Just count the samples in base file within the markers, usually every 10-20 minutes, with the file to be stretched, and figure out the percentage difference, whether to shrink or stretch. There is an excel spreadsheet with preprogrammed formulas widely circulated with room for about 20 marker segments. Copy the percentage difference, which might have 8+ decimal points, into Adobe CC or Adobe 3. Repeat for every marker segment. It is super easy. The hard part is placing the markers at precisely the right location, and Adobe CC with its wave form mode makes that pretty easy.