That looks a great little project! But its also shows the potential difficulties of using Tillet pads as they are so narrow in the centre. You'd probably have to use two smaller pads.
My only recommendation is to make sure they are isolated when you switch the ignition off (it didn't happen but I thought it likely).
I'm certainly tempted to invest in a more permanent solution but it might be worn rather than installed.
Democratic dissent is not disloyalty, it is a positive civic duty
Just don’t go out when it’s cold
yes im a soft old sod I no
Derek, you take the dog out for a walk whatever the weather.
I know they are unpopular for obvious reasons but you can't beat velour - warmer and you don't slide around. I'll leave now...
Fitted aftermarket ones 15 yrs ago or more - excellent even on cool summer morning commutes or summer evening blats back home.
I have a couple of Chilli heated waistcoats I used to use - still used in the trials car - they simply plug into a cigarette lighter socket. I have a bank of four in front of the heater under the dash, so the passenger can use theirs too.
If the elbowing from SWMBO becomes too much I may consider fitting one of these...
for now just thermal or silk base layers
As above, plus:
To answer a couple of your questions:
1. The pads are 30W each on full power so max 10A draw @ 12V. More likely to be around 9A @ 13.5V. The system has a 15A fuse as I recall, the main supply is designed to connect directly to the battery. The one I bought has 6 heat levels so has a control unit, the high/low type use relays to switch the two heat pads on one seat between being in series or parallel.
2. Each pad has it's own connector, the cables for the seat pads are long enough such that I have the connectors just below where the looms from the controller exit the rear bottom corner of the tunnel top. Full range of seat adjustment and easy to lift the seat base up and sit it on the tunnel top without unplugging it for cleaning etc.