Here is a resource (attached below) for finding combinations of straight FasTrack lengths that is more comprehensive than previously published tables (as far as I know).
This past December when I first started transitioning from only using O36 FasTrack switches to larger diameter switches and before I discovered the FasTrack Formulas Table mentioned in another post here on OGR, I made my own Excel type spreadsheet that offers some more options for combining the different available lengths of straight FasTrack than this other preexisting resource.
In the full length spreadsheet attached below, many lengths have more than one possibility. Here is a small screenshot sample from it:
Where there are multiple possibilities, the fewest number of track pieces is listed first, followed by no more than a few alternative options. As the lengths increase above about 12" there are more possible combinations for each length. In this higher range, I also discovered a few (maybe) better (IMO) options than listed in the other table.
I'm freely offering this information to the members of this forum as another resource, with the understanding that it is a work in progress, and that it may still contain a few errors. If you discover any, please feel free to make corrections and repost or let me know and I will. Also if you discover any additional combinations that may be useful to include, feel free to do likewise. Since, in my opinion, most of the options within the 12 to 25" range are easily extended by another 5 or 10" section, there are few useful length combinations beyond 25" included in this spreadsheet.