I can't seem to find it in DatEdit, so is there some other way to do this?

In flingy.dat, there are a few boxes that say things like 'top speed', 'acceleration' and such. There's also a dropdown menu that says 'Flingy.dat control', 'partially mobile' and 'iscript control'. If the dropdown menu is (by default) flingy.dat or partially mobile control, you can just change the top speed values and whatnot. If it says 'iscript.bin control', you'll have to edit its iscript using IceCC.