You should go ahead and use the Robart 615 retracts. 3 of my friends here in Denver, Co. have these retracts installed in 2 TF Corsairs and 1 TF P-40. These planes have been flying for the last 3 years and they haven't had problems with the retracts. All 3 have Robo-Struts and the gear rails were beefed-up in all 3 planes. The Corsairs weigh 12 pounds and 12 and a half pounds. The P-40 weights 11 pounds. These guy's are GOOD flyers. Any gear will cause problems if you are constantly slamming the plane into the ground on landing. I haven't read the forums on the 615 retracts, but I have seen them work just fine time after time in 3 planes with good flyers.

And yes I want one of these CMP hellcats.