One trick that has become more popular is filling the ends of the handlebars with something like an aerosol foam (expanding foam insulation in a can) or some type of silicone (like a tube of silicone caulking). This serves several purposes – it acts as a vibration damper to reduce handlebar tingling, and it acts as an insulator to keep handlebar heater output focused on the metal bars instead of the cold airspace sucking the heat away from the bars.
One company actually has developed a special damping gel just for this application. Called Bar Buzz Kill (what a name) it comes in a tube that fits right into your caulking gun. The custom-designed gel formula greatly reduces the amount of handlebar vibration, and users report being able to run the heaters lower than they used to. This can be used on all sorts of rides; ATVs, dirt bikes, street bikes, sleds, all of it. Check it out at
FrankInd.com on the web.