What if they fell at random?! and also... if there was the chance to get a xp for free, couldn't you just have different levels of it available to the different amounts of points. So, if you where positioned over 5th place on the table, you would get xp bonuses more frequently. You could also stop people under sergeant from getting the bonuses or something like that. You could also have a 500 xp box that acted exactlly like the 100 crystals box just gave you xp.

Fussy!!!!!!!!!!!!!!!!