Here are some more things to think about.

1. If you want to get as far away from nasty relflective surfaces then you should think about placing your mics exactly halfway between the floor and the ceiling.
DISLCLAIMER: This isn't all that useful a rule as few people listen at such a position and you certainly can't when you are walking about deciding where to place your mics. HOWEVER having said that I often have nice results listening at ground level to decide on front to back placement and then extending the mics to halfway up the height of the room, it's unscientific but it often works.

2. If you are recording an orchestra without spots it often pays to get very high and focus your mics at the sections you would spot if you had the time/facilities (woodwinds/percussion). Hypercardioid ORTF works really well this way. The directional focus of the mics brings out the detail in the more distant instruments.

No hard and fast rules there but a couple more things to think about.