Yes, I trained with HR. The power was a SWAG, back then I didn't even look at speed on longer rides. Only time and HR. Numbers from now are actuals. I use WKO4 to crunch them (that's also where I looked at the comparison between my current HR Zones & Power Zones). The only non-SWAG comparison I can make is back then Z2 on flat ground was roughly 42x15, now it's 52x21.

Getting back to the OP. The point I was trying to make was that I don't notice a big difference in recovery from Z2 rides, IF I stick to the zone. You can't really do that on a group ride. I do feel like I need more rest after intervals at higher intensities for them to be adaptive.