Sorry Viper not got a clue as to modern Morgan construction.
If the hole in your pic is a drain hole, then I might use a hand held twist drill a little under the size of the hole, twisting it with my fingers or perhaps old style carpenters hand operated drill to try to clear the sealant, taking care not to damage the perspex.
Though if there is indeed a drainage system chances are that other than the hole the rest of the system may be gunged up...?
I guess it takes time to resolve teething issues with a hand built car.
My mid 80`s +8 seems to have been reasonably water proof, even in the worst of weather over the years, so it should be possible to sort it out..?
BTW many a Porsche convertible leaks water even to the extent of destroying under-seat located ECU`s... EXPENSIVE..!
Good luck.
