I use a "standard" A5 kneeboard, with lots of plastic pockets inside, strapped to my knee. I've been very happy with it as I tend to do long distance VFR.
However a few years ago I rented a Bdog and got checked out in aeros again (I hadn't done any since the UAS). Went into the first manover and of course the board flapped open
Still at least nothing fell out.
