This was a little hard to get right for my first whack at it, possibly because my rocket is an attempt at solid SSTO which maybe this plugin isn't designed for initially?
Here's what I ended up with after 8 improved guesses and then some manual tweaking, let me know if it looks roughly optimized. Improved guesses only got me down to about 600km apogee, needed manual tweaking to get better than that.
I locked sensitivity at 1.0 because otherwise I saw it trying to throttle my SRBs. I locked Start m/s at 10 because the improved guesses started going negative. I locked pressure cutoff and manually set it much higher because improve guess didn't seem to change that number but it originally occurred well past engine shutoff. I locked turn angle and had to start manually increasing it to 42 because improve guess kept it around 23-25 which wasn't nearly aggressive enough. Now I'm still slightly overshooting my target apogee, but 250 apogee / -78 perigee is much better than I could do by hand (previous best was -350 perigee), before blowing up from getting too shallow and hot. Probably a product of my ship design. Maybe need to limit my SRB max thrust? I'm at the point where if I increase my turn angle by 0.5 I overheat and blow up right before engine cutoff
I'm also aware I'm about 300 m/s shy of orbital velocity but this is close enough for me (second stage is all nukes, it's a Tylo visit and return mission).