Myself, I would forget the interior water filter system. I would go to wallmart and pick up the exterior water filter that attaches to your hose. Its a one year throw a way unit for about $15. If you want to go with the larger filter and canister system, I have see people using them also on the outside of their unit. They would make a stand for the filter so the canister would sit upright. The old old style christmas tree stand works great. Either way I would not mess with cutting lines inside the coach.
Retired and never looked back