We have 30+ years of boating on Winni, never been stopped. Our boats do have NH on the bow number but I don't think that the Marine Patrol has a "harass out of staters" mindset.
I think that you have only 30 days on a out of state reg.
https://www.boat-ed.com/abc/abc_spec...dfs/nh_law.pdf
Maybe a call to Marine Patrol stating that you have a PA bow number, noting the past stops and asking about how to avoid such. My experience is that they are pretty reasonable folk.