Hey its nice of you to drop by Lindsay, welcome any time. Actually its gotten quite quiet around here recently.
Anyway, yes we do have some surprisingly similar numbers. Indeed I used to use 43/173 HRR too, but then I went a long time never seeing a 170 although I have since observed a max of 171 once in the last few months. I also never check my RHR so the numbers I'm working on this year are 45/170 which gives me the 144 top to UT1. I've never had my VO2 max checked - much too hard! The only other "excuse" I have is from a full function medical I had when I turned 40 when I was told I was fit enough, but had relatively small lung capacity for my size (measured in litres IIRC ?? and I was more than 1l smaller than Matt Pinscent) ...nothing bad just smaller than avg apparently...which cant help. Interesting thought on higher threshold - maybe why I preferred training the SS stuff harder before? I'm still convinced its all far too influenced by the vagaries of the mental state rather than just physiology - its just all so much more fun and doable when you're on a roll!
I agree with your thought on aiming higher for your next 2k. Just take a second out of the 2nd/3rd 500s and see what happens. Its gonna hurt of course! Also I wonder how much its about sub 7 being the accepted goal...and when you have 3 or 4 other competitions to do on the same day you're not really up for going to failure on any one of them? Just holds you back a fraction. Sound like fun though...