MIMF

I am progressing on a pair of bass uke builds.

These will have the black polyurethane strings. The bridge on the commercial products look as if the bridge is much beefier, has more gluing surface, and is located further from the sound hole.

The concept of the surface mounted piezo is to pick up body vibrations.

The concept of a underbridge mounted piezo is to pick up string vibrations.

Since the piezo is producing most or all of the sound, should I put in a really heavy bracing? Use a heavy bridge plate? Ignore any sound from the body?

The Pahoehoe strings are rather low-tension, so you don't need to beef up anything. It will be worthwile to strive for a decent non-amplified sound, I converted an existing baritone 'uke into a bass, and it is certainly loud enough for practicing.

Thanks.

While I have your help, what did you do for compensation on the strings?

A quick job with a ruler says: going gradually from about 8 mm compensation for the E string to about 4 mm for the G string.
If you stray to the forum at ukuleleunderground, you can search for a couple of threads about u-bass conversions (including my humble efforts).
I'll give you a more thorough answer tomorrow (bedtime in this part of the world).

So here is the result of a more thorough measurement: Scale length 48.7 cm + 9 mm for E, 8 mm A, 6 mm D and 5 mm G (give or take a mm, as the rounded saddle makes it a bit difficult to see precisely where these fat strings touch).

Thanks! I appreciate your help.

I have a couple of busy days ahead of me (day job!). I won't be able to do much for a while.