Hi Andrew,
I have been flying for just over 12 months, and have used my flymaster sd gps on both leg mount and harness mounts. I prefer the leg mount as it keeps the vario out of the way but visible when necessary. Haven't used it on my flight deck as yet, leaving that for this year if the weather ever turns to our favour
Andrew
As has been said it is very much down to what you are comfortable with, at the moment the vario is less essential given I am still in the ridge soaring league rather than looking to go xc (yet), and I found it better suited me on my leg, given I usually wear a flying suit with Velcro that stops it from moving about. I'll probably change my view later in the year when I have a few more hours under my belt!
I intend on joining the DSC is year, so look forward to seeing you in the hill-we can compare notes!