Two questions, but first an explanation:

Previously, for some reason, I thought FTP tests were supposed to be 30mins. (I think the idea came from the Joe Friel Power Meter book) Then taking 5% off to get the hour value. That is what I have done in the past. Breaking the 30 mins down into 5 minute intervals to monitor evenness and progression. (I do a lot of 10mile TTs so it is also a more natural and real world test for me).

When I started TR (4 weeks ago) did a ramp test and that came out at 235. About right so I stuck with that.

Tuesday I did the TR 20min FTP test, but actually started the session in that initial 5 minute loading, and

bridged across the 5 minute rest in resistance mode, so that i did a whole 30 minutes in resistance mode. I averaged 249w for over the whole 30mins and 251W over 20 mins. This gave me an FTP of 238. (The 5 minutes were 244. 246, 246, 248, 255, 255W)

Question 1: I assume the 30min value is a better test. is that right?

Question 2: Does the fact that I did very similar values every 5 mins suggest I could be higher for 20 mins?

Question 3: I assume I am best taking the latter 20 minutes when the average was higher

Question 3: Is a 5% reduction used for the 20min test. Is 5% off the 30 min still one appropriate.

Thoughts please, thanks in advance