Totally not trying to contradict you though Glen, you're the profesional; any new riders please listen to Glen.
But personally I use the outside two and get easily stand it up without hurting my hand.
I use the inside two mountain biking so I can hold on to the bars, but on the moto I find it nicer using the outside. Maybe I've gotten used to using them for 'force' holding on to the pushy?
I love being technical though, and technicaly, outside fingers have a firmer grip though it's hard to tell. Do the "crush your friends arm" test if you don't beleive me, haha.
None of my riding instructors ever told me that, unless I missed it. Just after getting my L's a mid-30's guy on a GSXR told me to never use both brakes together, he said it's a death wish... use all front or all rear, and avoid using the front at all costs. Didn't sound right to me so I ignored it. But that's a worry ay.providing some drag thus keeping the back in line when your braking hard in a straight line or pulling it in when your cornering.
Is stuff like that set in a syllabus or are instructors allowed to chuck a few of their own points in?