Try wrapping it with reflex insulation, its a reflective foil with air bubbles, works great as insulation, you can make a cover out of 4 inches of foam. Mine works for me and I am 6 foot. I replaced the plug with a drain valve, use adapters. I use an 15 amp 120 Volt immersion heater with a temp controller and small pump running water through a filter that sits in the tub. turn of the power before taking a plunge.
It’s been so hot and at D&B it’s about $110 for this size, gonna get one to cool off .. thanks for the “sizing”. How do you keep the water lean and how often do you dump and re-filled?