I suppose you could drill through the shroud and tap the underneath of the barrel, but it would have to be done very carefully.
I have a feeling this is how the second series of the Model 10 was adapted with the under-barrel weight - ie retrofitted with no change in the (brittle) shroud moulding at the manufacturing stage. The moulding seems to crack at this point quite often, so it probably should have been strengthened first.
Personally I would leave well alone and if you want to make the front of the pistol heavier for shooting, find a reversible way to attach the weight temporarily.