I would keep the Top Kart as long as the chassis is not too worn (flattened) on the bottom, bent, or sagging. Though it’s a few good years old, racing a lower HP class means that you haven’t put the thing through the wringer.
When you make a change to your program, as you are, going from club to a little traveling, you want to keep things consistent. This is so you can utilize the experience you have on the current kart to the new tracks. Trust me, last year, we did most of the USPKS races for the first time on a new frame. This meant unknown kart, tires, and tracks. We even changed classes, so we really went in blind. As a result, we didn’t post better than 11 all year. So keep it simple when making changes.
As to the change in chassis performance, at the top level of karting in the U.S., OTK doesn’t have the exclusivity on winning.
So I’d keep the chassis for now, and put some aside for when it’s no longer working for you.