In general nicads need to be discharged all the way every time, right after your run. Not familiar with that battery, but I would suggest discharging at 20 amps, maybe more. At least with the 1200-1700 Sanyo nicads I used back in the day, discharging them at a high rate increased voltage under load after a few cycles. What was called pushing or training. Which is where matching cells started I believe, so you could discharge hard without damaging weaker cells.

And the higher you charge them, the better the punch will be as well. Suggest a 6 amp charge, try to have them peak about 10-15 minutes before the race, then repeak at 8 amps right before hitting the track. Or higher at the risk of reduced run time and battery life, but more punch.

Store them discharged. Some would dead short them before charging, but I think that depended on which nicad. I discharged to 0.5 volt per cell with good results.

Of course with all of this weak cells do not survive. If I remember correctly back in the day my battery matcher would start with 5 cycles to train them before matching, and some didn't survive. But the ones that did performed much better. So I guess if you can't open the packs to rematch you might have to lower the amperage some, but at least be sure to discharge them all the way every time.
Good luck!