There are rider types that do “better” on Half Monty compared to Full Frontal. The main one being Attackers, secondarily Pursuiter.
We have found that many people for those rider types get artificially high FTP and MAP values from Half Monty, while those who are more diesel type (TT’ers / Climbers) might see the opposite.
Ramps will always give artificially high Sustained power values (FTP / MAP) for people who are “anaerobically inclined”- attackers and pursuiters. We have found that our heart rate-based estimates will give more accurate (lower) values for those rider types.
When comparing your own Half Monty to Full Frontal results, it’s useful to look at the difference in Peak Heartrates. If your peak heart rates are relatively similar, then you had similar freshness on both tests.
The 6-week difference in training could explain some of the changs in fitness. Really the only way to know for sure is to see how you feel on your next hard workouts. It’s always okay to dial the intensity down for FTP and MAP after a new test when going into hard workouts right after increased numbers.
There are a few tweaks that we have in mind to improve the accuracy of Half Monty, but the Gold Standard will always be FF.