Grip Heating Elements - Heat loss on left grip?

I just ordered the Dual Star grip heaters and noticed on their site that they sell shrink tubing that on recommended for use on aluminum bars to prevent conductive heat loss. Has anyone here experienced heat loss in the left grip without an shrink tube insulator? Does installing the shrink tubing mean that I need to get a throttle side (larger) grip to now fit on the left side?

If I need it, I'll call and add it to the order before it ships (shipping next week when another item is due to be available).

Thanks in advance!