Used a 1/4" dremel sanding drum to drill down to the plugs in the drain hard points, and fitted the drain plugs to both main tanks and the sump tank with teflon tape. Contemplate the result, and find it unspeakably ugly. Decide to make some fairings to hide them. Backfill the surround with modelling clay and cover with box tape. put a conduit sleeve over the taped drain plug and make a vaguely aerodynamic shape over it with modelling clay. 2 x BID and 1 x 4oz over this, overlapping onto the fuselage/strake bottom.