Part of training for 'THEM' involves the wearing of the uniform of other patrol members, so while sometimes you will be wearing your own boots at other times you will have to wear boots belonging to another 'THEM' trainee. So I would suggest that as soon as you get there you try and ensure those in you your section have roughly the same size feet and if atall possible make sure you have the smallest feet. If the others have bigger boots you can stuff newspaper into them to help with the fit, on the other hand(foot) if they are too small you be in a great deal of difficulted while on long marches.
Hope this helps with your selection
now take your hand out of your sock
I'll add to that that the likelihood of two of the others loaning you boots at the same time are very slight - nobody likes hopping around on an op. My best advice to you is to train your feet to wear either two left or two right boots at the same time - this could also save some time swapping around, as well.