None! The SF turbo head, and the SF turbo head adapter...and my adapter to their adapter, give more than enough mass for cooling. The entire light will get warm, after say...30 minutes on the high setting.
The driver that's taped to my test plate has endured 10 hours at 3 amps, and it has suffered no ill effects. It's really a nice driver, and better still at less than $5 each.
I'll add another photo later today, showing the two adapter pieces, for those not familiar with the SF turbo head, and my oldy parts line-up.........