If I come out tail heavy this will be one of my top mods to "add weight" If I'm wrong just chime in and correct me. There are four ways to add cabin heating, forced air muffler heating from a wrap. tapping into the radiator, forced air cooling from the cylinder head of the engine and drawing from a battery, I'm not gonna talk about the last option cause that is just stupid. All of that heat has to be controlled from a damper box that vents the air outside if its not used to heat the cabin. There is a risk of carbon monoxide poisoning by tapping into the muffler for heat. here is how challenger aircraft draws heat from the cylinder heads. http://ultralightnews.ca/challenger_accessories/challenger_incabinheat.htm

If it comes out heavy, add weight somewhere else. There is something you don't get here. Recover the tail in Oratex.
The CO risk is the very reason to heat electrically. UK Maxer's have for twenty years used the 1A current draw requirement to power electric insoles.

I have used liquid heat (from a 582) and it worked fantastic (easy to control and remained stable through the flight envelope). Tried the exhaust can wrap idea, but found the heat output would quickly vary with power setting (no thermal storage capacity: i.e. cold descents and hot take offs if you will).

We have Challenger folks using the system you mention and they love it. However, they are also running fan cooled birds to help drive the flow (even air flow on the engine and sealed from the CO areas of the exhaust).

With your free air, you have a bit of a snag there.  If you duct around it all (or near it) you could restrict flow and create hot spots on the engine or worse.  Maybe you could duct it (from a safe distance away with a pulling fan) but then again you are in CO territory.  Just my 2 cents worth anyway.

Battery operated sox; they take a 9 volt battery.  Buy two pair, use one pair for your feet and one pair for your hands. Or wait for global warming to kick in.They make those chemical heat packets, make a vest with lots of pockets for a whole bunch of packets and wear the vest next to your skin with a coat over them. Move to Australia in our winter cause it is their summer.  

I just park my AirBike anytime it is below 70 F.

I have to duct my free air cooling (As due to the position of the redrive pulley on my Kawi 440, it will not actually get much cooling). I am thinking of putting a baffle in to allow me to send some of that air to the inside of the plane instead of spilling off the side.

Quoted from aeronut

Battery operated sox; they take a 9 volt battery.  Buy two pair, use one pair for your feet and one pair for your hands. Or wait for global warming to kick in.They make those chemical heat packets, make a vest with lots of pockets for a whole bunch of packets and wear the vest next to your skin with a coat over them. Move to Australia in our winter cause it is their summer.  

Brilliant, global warming powered heating, I can make myself feel good while doing nothing!

Or just burn more fuel in an overweight aeroplane. Your choice, of course.
, But the energy you need to dissipate to make the regulator work is twelve watts that would warm your feet. But that would be stupid.

Before I added cabin heat I just used the "Hot Hands" hand warmers and foot warmers (dry chem stuff).  Works great.  Also had a friend make it home once when he started getting carb ice on his 447 with Bing.  Strapped a few "Hot Hands" around the carb and it did a great job.

Ask those people in Minnesota this morning. I will bet they will tell you where to go to find a little heat. And right now. LOL.  The coldest that I have ever worked outdoors in was -38F. I defiantly would have told you where to go for a little heat that day. That is why I am in Florida today.  

If your 447 or 503 is fan cooled,  you can get a heater kit from Uflyit   for $175.

http://www.uflyit.com/heater.htm

These guys have some good ideas to stay warm as well.  I know it deviates from your CG portion of the discussion though, but might be of benefit to some.

http://ppcflyingforums.com/forums/showthread.php?t=10973

I know several folks who use these will good success:

http://ppcflyingforums.com/forums/showthread.php?t=6985

Before I add cabin heat to my AirBike, I would need to add a cabin.

Paul Fiebich

If you add cabin heat to your airbike you have went full blown nut  job. No chocalte butt holes.for you!  If you do it anyway your a rebel