Neil,
If I remember rightly, the 2391 practical inspection involves a rectal probe of biblical proportions.
I've just checked the bible that I keep next to my desk, and it's proportions are around 225X150X40mm, and I can see that no amount of KY jelly or peanut butter and marmalade is going to make an inspection comfortable. They have a nerve calling it 'practical' really.
Anyway, good luck. My advice? - don't plan anything too sporty for the weekend.
H