I can crawl through 18″ cautiously in my 1775 Impact XS. I don’t know the exact draft of my boat but If I see 1ft or less on my ducer then I’m either bottomed out or about to be in short order.
Your glass boat is heavier, I would imagine 2ft or more would be needed. If you know of an area to test it out cautiously I would do so, just so you know. Drive slow, trimmed way up, and when you nudge bottom take note of what your ducer reads and go back. Once that keel gets buried it can be tough to get out. Plus, glass boats and hidden rocks don’t mix from what I hear.
Had to use my prop in reverse once to get out of a mess I walked myself into forward. That little adventure resulted in a new impeller, but fortunately the prop was okay. in fact, hammering it in reverse through the mud resulted in a very shiny polish effect on my stainless prop and it handled surprisingly well in reverse in deep mud. I wouldn’t recommend it, a hidden log or rock would’ve ruined my day and been painful on the wallet.