I put the mattress warmer at the bottom of the bed because I get restless leg at night sometimes and the heat on my calves really seems to help. My husband has cold feet of torture so it's a win-win.
Here's an except of an e-mail I received from ElectroWarmth (6/2014) when I asked about a queen-size 12-volt mattress warmer for my parent's camper van:
"We do not have plans on bringing back the 12 volt queen. However, the 12 volt T36, 36” x 60” might be an alternative. If you position it sideways, you would have the width covered and then heat coming up 36” on the bed. Since it is a flat warmer that pins to the mattress, you could position it low, middle or higher up on the bed as preferred. It would be controlled by just one control, but still it is an option. It’s not possible to position two warmers side by side lengthwise, as there would be overlap and that is a safety issue."
I might be a little paranoid about overlapping wires (is it like "crossing streams" - maybe!) but I think as long as you keep the warmer taut, either with pins on the mattress (as recommended) or attached to a mattress pad, you should be OK no matter where you locate it on the mattress.
I was thinking about sewing two warmers together (avoiding any wires) and using it as a single unit. I would have a controller for my side and Tim would have a controller for his side - except there's no 12-volt jack on Tim's side of the bed. I suppose I could orient the pads crosswise so both 12-volt plugs are on my side of the cabin, but that's too many wires going too many places - just the one set of wires is a drag. Would I trust Tim to kludge something together...hmmmm...that wouldn't set us on fire in the middle of the night...hmmm.....
Also these goofy warmers are expensive enough as one - let alone two! It would be nice though....
I think ElectroWarmth made a mistake discontinuing the queen size - they could have partnered with teardropshop.com - I bet they could have sold 1 for every 3 or 4 Little Guy and T@B sold - not to mention other walk-in customers.