I don’t have any original advice on pacing beyond what you’ve probably already read here How to Get The Most out of Full Frontal – The Sufferfest with the critical part being this bit:
"A well-paced 5-minute effort is one where 2.5 minutes in you start thinking, “I might just be able to hold this, but it will be close”. If you get to the 2-minute mark and start questioning whether you’ll make it out alive, you went out a little too hot. If you get to the 3-minute mark and think, “I have some energy left in the tank, I need to up the pace” then you didn’t start out hard enough. That said, starting a little bit easier will get you closer to a perfectly paced 5-minute effort than blowing up spectacularly 3 minutes in.
As far as cadence goes, your best bet is to be a little higher than what you consider your “optimal cadence”. If you normally sit at 90 RPM for hard efforts, ramp it up to 100 RPM. Remember, you still have a 20-minute effort and a 1-minute all out effort on deck after this. If you’re grinding out a big gear at a low cadence you can very easily thrash your legs, which will make the next effort that much worse."
As an alternative, you could just do the Half Monty and get new MAP and FTP with a lot less pain.