RE: Tuttle fin in Deep Tuttle box
The fitting procedure is the same.
Deep Tuttle into a deep Tuttle box requires the same amount of "fitting" as putting a shallow Tuttle fin in a Deep Tuttle box.
You cannot put a Deep Tuttle fin into a std. Tuttle box unless you cut the top off the Deep Tuttle fin root so that it's now a std. Tuttle fin root.
I think your Isonic 145 has a deep Tuttle box, and there's no problem (other than the std. amount of "fitting of the sides and front/rear tapers) in putting a 52 cm fin with a std. Tuttle root in the DT box in your Is 145.
You will however need a set of longer fin screws.
Using a bar of bath soap as a "marking medium, and a file to remove only the shiny black spots where the root makes hard contact with the fin box, it should take < 10 min. ro fit any fin.
If it goes in too deep, you can use clear packing tape to "shim it" back up, but a more permanent fix is to put some filler on the front and rear tapers, tape the filler to the radius while it sets up, then fit your fin until you have about 1/32" draw.
Hope this helps,