It is an excellent idea to fit either brass or wood dowel inside the lower masts to provide extra strength.
As I recall the t'gallant masts on the 'Constitution' model are very fine and susceptible to pulling out of alignment when rigging, even with the lightest touch.
The problem with wood dowel is drawing it down fine enough to replace these poles, at the diameters involved this would also be prone to breakage.
Very fine brass tubing can be obtained down to 0.3mm diameter, and I think were I to do 'Constitution' again I would be trialling such as a replacement.