I did one once, but memory is flagging. For sure, you'd have to mill out a slot wide enough to accommodate the fore-and-aft positions of the strings. Before you start the project, you'll want to know how far to move each string, so read this piece:
Then consider telling the customer what I usually try to do - tiples don't exactly play in tune. It doesn't cut much ice with most modern players, but it is the truth.
Indeed those bridges are too delicate, so be sure there's no crack between the pin block and the saddle area. . .
Along the lines of "tiples don't play exactly in tune", the second and third courses have an octave string. So there is going to be a conflict there, as well.
Perhaps you could pop out the fret, and take the widest fret you can find, shape the top to be intonated, and then put that in place?
But it's a tiple - these are not fine tuning instruments, you just tune them as close as you can and play until you give up and get a ukulele. :)
And here is a photo of the tiple with the new bridge installed. I intentionally made it a tiny bit smaller than the original just in case someone wanted to reinstall the original bridge. I was shocked to find that the plain and wound strings in each course intonated the same!
Wow! that looks great! Is that fret wire for the saddles? If so, how did you slot for the tang? once again, great job!
That... is just brilliant. Could someone (Hello Frank?) please put this on a website for the 3 other people who may ever deal with one of these things?