I put all my radio gear into a tank bag, ran power into it from the socket under the seat and put the ptt on the outside left of the bag, that way I could take the whole set up off the bike with the bag as I only needed it on a trip to Morocco.
I've tried all different places and at the end wanted to make sure that I do not have to use my thumb to press the PTT - as it would technically require me to lose grip on the handlebar.......... this became apparent when we did a lot of dirt riding........
So finally - ordered a smaller PTT and placed it on the Clutch lever - this means that I can easily use my forefinger (I normally ride with two fingers on the levers) and ith very little effort - utilise the PTT for COMMS.
(unfortunately my bike's in the UK an I cannot give you the exact pic of the install - however the pic below shows the position and the one below that the actual PTT I bought off eBay)