Installing new stabilizers on a 2006 Dutchman T@b

@Carolyn, after reading your question, I recalled the below post.  @Grumpy_G provided some potential solutions for consideration.  I agree that the stabilizers were likely installed with carriage bolts inserted through the floor from inside the trailer.  If the attempted nut removal results in the bolt spinning around in the hole, then it would seem that accessing the bolt head from inside the trailer is the best way to go, but your son will still need to figure out how to remove the nuts from the bolts.  As already suggested, accessing the heads of the bolts will require figuring out where each is located (i.e., where inserted through the floor.)  Definitely not a fun task.  If the nuts are seized (corroded/rusted?) to the bolt thread, the suggestion to use a screwdriver to assist with removal of the nuts is a good one.  Your son could also try spraying some B’laster PB Penetrant and Rust Remover on the nuts/bolts (breaks free rusted or frozen parts.)
  
https://tab-rv.vanillacommunity.com/discussion/15888/2019-tab-320-stabilizer-bolts#latest