If your water heater is working within it's normal ranges try adjusting the shower valve. I'm not sure which type faucet came in your trailer, but most shower valves made these days have an anti-scald adjustment made into them. Look at the manual and manufacturer's data sheet to see if your's does.
If it does, it's a simple adjustment. You have to remove the handle from the faucet, remove the escutcheon trim, then adjust the valve limiter to where the max hot water temp suits you (I like 120F max as mandated by building code). I use a cooking thermometer to check while it is flowing. Easy peasy. No more pink behind when you move around in the shower.
I'm a big guy too, head touches the top, bottom & arms touch the sides when I move around. DW says it sound like I am wrestling someone in the shower.
I have done this adjustment on a few shower valves myself. (I'm a retired/part time general contractor) If you get this adjusted correctly, the water will still be hot at the sink faucets and the shower's hot water supply will be ample enough for two showers in a row, safely.
I hear there is a tropical storm in the gulf today. Headed inland soon?