Hi Hitch Pin,
We've had a SLX BH 154 for 1 1/2 years. Agree, one of my first modifications was replacing the very thin plywood with 3/8 inch under the seats. I also added a ladder to access the top bunk (CampingWorld purchase), replaced the table legs with one of those swing systems for $50. Minor stuff like a paper towel rack and cutting board over the burners for more counter space.
Prior to a 14-day and 2,000 mile trip across New England I converted the shower area to a temporary closet with nice baskets for clothing and a hamper. It worked great. Since then I need another modification for a dog kennel. It fits right over the tub on top of plywood. The door swings out and now the shelves are on top. We'll test out this weekend.
Our family of 4 really enjoy the camper. Sure it's small but it's comfortable with all the amenities. When camping we're usually outside most of the time and just need comfortable sleeping and ample storage. No plans to upgrade. The 154 is light weight, fits in the driveway and is pretty low maintenance.
Have fun with your new purchase.