I just bought a Cactus RF60 flash and a V6 transceiver, downloaded the instruction booklets, and though it works in 'normal' flash modes, it does not work in High Speed Sync mode. I've looked in the booklet many times, looked online for information, and I cannot find any workaround for this problem. Nikons don't have this problem, and as far as I know, Canons don't either, but Pentax certainly does.