Did you get the system 3 purification with your tub.
I like the seat by the stairs too but it is just a little bit too shallow for me. We have the sports therapy package so my favourite seat it the one on the filter side that has the pulsating large jet rings, hip, wrist and calf jets.
Our tub tends to warm up quickly too as it is almost too well insulated and the heat from the circ pump tend to stop the temperature from dropping. To cool the tub on hot days we have a large umbrella over the tub, stick broom handles under both sides to leave a 1 to 2 foot opening, and we open up the pump compartment to let some of the excess heat escape. If that does not work fill up some plastic milk jugs with water and freeze them with the caps on and put them in your tub. this will cool down the water and it will not add to or dilute your spa water.
What part of the country are you from? We are near Vancouver, BC Canada. Enjoy your tub - We love ours