QUOTE (I Said)
(The map will need alot of fixing up, as the terrain used in RA2 / YR and TS / FS are very different, so be sure to go over the whole map looking for errors, etc.).

It doesn't make FinalSun crash. The Overlay just appears in FinalSun as "0x2" or something like that, for some odd reason. But yeah, make sure you delete all overlay's and stuff before you even think about playing it in-game.