hey rob.. I was searching and found a few posts regarding differences between the PA50 I and Pa50 II. Since i don't have an 'I' i can't verify any of this.
One thing that will certainly restrict the RPM of your engine is a short exhaust-open timing. This is the period of time, or of chankshaft rotational degrees, that the export port is open.
The PA50 I seems to have a shorter exhaust-open time than the PA50 II. You could check it by removing the sparkplug and muffler, shining a flashlight into the exhaust port and observing through the spark plug hole. Turn the flywheel by hand, make marks on the flywheel and measure the total angle (before and after bottom dead center) that the port is open.
It's worth taking a look, imo, because you're spending money towards performance but may get little or no results in return.
The port on a PA50 II is open for a total of 130 degrees.
The port on a PA50 i is open for 115 degrees.
The fix would involve grinding away something near a millimeter or two at the top edge of the exhaust port so it is open for a longer period. I can't predict for sure that your bike will never see anything near 30 mph due to this porting difference but it may not.
This fix is cost-free, has been applied and tested on the PA50 II and will improve top end power on virtually any 2-stroke, within limits.
If the timing is as i stated, and you feel like getting into it, i can post some hints on how to go about it.