i was dming last week and one of the characters has 2 immovable rods, he used them to get 20 feet in the air and placed them a foot apart. next he got on top of them and and began to fire his light crossbow, i said hold on a minute, you have to make climb checks to pull yourself up and balance checks to see if you can fire the crossbow without falling off the rods, he disagreed and the debate was on, what would you fine people rule as to firing a lightcross bow atop 2 immovable rods?