I have completed the next section and updated my WIP at
http://www.grimsrud.net/TAS/Captain_Skyhawk_WIP.fm2
Note that there is still a bunch of junk input at the end. I did manage to save 145 frames from your WIP. I think most of the savings came from getting to enemies from the bottom faster. If you pull up, then dive there are a few frames when you get to the bottom where you can actually shoot lower. For example you'll see when I get 2 enemies that spawn from below I bounce up in between them, this is so I can get to the 2nd one earlier.
I had a few more points to start with, but when I saved a few frames I ended up with the same score you had. At this point I'm almost thinking the best goal would be a primary goal of time, and a secondary goal of score. I feel like it's a bit of a waste to lose frames just for the score, but you'd still want to attack the enemy fighter mercilessly to run up the score. Just a thought.