I’d burn matches on those 2 climbs. With only 2 climbs of 2:00 minutes and a total time of 20:00 for the event, there is no reason to save any energy. This should be a pretty flat out effort similar to how you feel after a FTP test. MTB will force you out of a constant effort because the trail will mandate micro rests. Though short, those small rests make a big difference. This is how it differs from road TTs. If it were me I’d make sure and practice what effort I can do up and over each hill and whether I have time to recover right after, even if it’s only 10-15 seconds that’s plenty. Then, I’d session tricky corners and study lines to ensure I’m optimizing my speed out of corners. It matters more your speed coming out of corners than the speed into them. Also look for spots were you can “place” your braking instead of dragging your brakes. Placing your braking for a couple seconds if faster than dragging your breaks for 5+ seconds.
You have the benifit of the trail being close to you, so you should know every hidden line of that trail, which will be the un-worn path in places that most people won’t take or know about. You’re looking for speed and not efficiency (opposite of an XCO or XCM race), so the best lines are likely through obstacles as opposed to around them. An MTB TT is a different mindset when looking at the trail and is more of a XCC short track effort.