I just recently constructed a 39 degree with True Temper Lite XL shaft and Winn Excel RF grip. The feel is exactly the same as my Ping G10 32 deg hybrid (and I love the latter). I made the shaft length 38 inches based on running a swingweight calculator program. The calculated swingweight (given that the head is 249 g and using a Winn Excel RF 42 g grip) was D0 with either a True Temper Dynamic Gold or TT Lite XL. When I put it together, it weighed in at D2 (a point of interest is a True Temper Lite XL adds 2 swingweight points vs Dynamic Gold because less weight is on the butt end of the shaft).
The recommended shaft length of 37", a standard 52 gram grip, and a Dynamic Gold shaft calculates to a C3 swingweight. With the 35 deg club, it calculates to B9 with the same shaft length.
My personal recommendation would be to build the 39 degree club with a 38 inch length for men and 37 for women and do the tip trip same as a six iron.