Where do the leads of the main Top Sail bowline bridles belay when they reach deck level? I plan for these leads to be descending to the deck from single blocks tied to the aftermost fore shroud a bit below the futtock stave. Does this seem correct?
The main topsail bowlines probably belay at pins in the caprails along with a lot of the other topsail gear. There were probably round fairleads seized to the shrouds to guide them (we have plenty of spare fairleads, nice little lathe-turned items). Your lead, to the aftermost fore shroud, is a logical option. From there, the line would follow the shroud down to the rail, possibly going through a fairlead somewhere above the fiferail.
In general, very little of the rigging is belayed in the middle of the ship, most of it was led to the caprails.