Hey iplayfast,

I'm pretty sure, that won't be possible.
As the resin floats on the water, a created Island will also float and not stay at the same height with rising water.
Also although the printer doesn't exceed any force on the resin, wind, surface tension (or some jedi) could make the Island drift away.

Fortunately this also enables the PeachyPrinter to use really small support structures as there is virtually no weight to be supported.
Considering overhang, You probably can print full 90°, thats something to test for one of the guys that already have a printer!
I hope, this answers your questions.

Greetings,
quertz.