I agree with everything you wrote about R pace, except *I* am refering to I pace. R pace is supposed to be significantly quicker, close to mile race pace. For you, that would likely be roughly 5:40 pace.
_______________________________________________"I'll blow up trying to run 3-5 min repeats at 3-5K pace for 6-8K. Lets say I can run a 20 min 5K - or a bit under 6:30's. I'd have to run 8-10 1/2 mile repeats at about 3:10. Ouch. That would fry my legs for a couple days. "
______
It's good that you know that. Everyone is different and you need to figure out what YOU can handle. The goal is NOT to blow up and take a couple of days to recover. From my experience dealing with runners, 8 shouldn't be a problem. You can run 6 of them without ANY breaks (I call that a race), it's odd that you can't do 8 with 7 2:30 minute breaks in between.
-----------------------------Baron Von Speedypants
-----------------------------RunTraining articles here:
http://forum.slowtwitch.com/...runtraining;#1612485