I also don't see this as super high for a true training ride (as opposed to a recovery or endurance ride). Relatively short course, fast time, plenty of up and down in the profile. My average would be right about there and V, you and I are all about the same age (putting another nail in the 220-age formula).

Here's a way to estimate your LT and really get those zones dialed in a bit more:

http://www.ultracycling.com/training...ing_zones.html

I'd still go with true lab testing if it is available to you, but this is a good interim measure (so to speak).