I have a similar situation. I either use a 'flat' sewer hose (Level Upp) but good luck finding it these days. Or I use a 90 angle and the run the hose in a 'U' shape and then down through the hole. Or I use the 90 angle into a 12v macerator and several brass angles to get the output 1" hose down the tube. Good for long stays but very difficult and messy to disassemble for travel. I suppose I could use the 'Sewer Solution' water powered macerator, but the first and only time I tried it it clogged up, what a mess that was.
Thanks for your comments. I think I finally solved my problem by removing the tube and using a very short piece of sewer hose. I was able to get the sewer hose on the tank outlet with a lot of difficulty. It will not come off now. The other end I attached to a similar outlet fitting as the tank. I fastened that piece with a steel plate to the bay. Now I have a fitting similar to the tank outlet except it is now on the bottom of the bay. This will now work with either my sewer solution or a standard hose fitting.