I glued the corner braces and gussets in place on both ends of the wing [St.2 1/4 & St.57 1/4]. On my copy of the plans, the brace at St.57 1/4 does not exist - due to poor copying, and YES I do have a bone fide copy...
The spar fillers were then glued in place. I used 5/8 x 9/32 spruce for the front spars. Rear spar fillers were used from St.57 1/4 as per plan. I then made a primitive jig for routing the fillers flush with the ribs. For this to be accurate the ribs have to be level with each other along the wing - I used to long aluminium straight edge to initially check. If the ribs were not level, I would have used the top of the spar [guaranteed straight - or should be!] as a reference point and not the rib.
The spaces between the aileron-well ribs, and any cloaking of the aileron well is not referenced anywhere in the literature. But it was obvious the spaces between these ribs needed bridging. I did this with 1/4 birch ply. As per pic, I used popsicle sticks as a kind of nailer while the T-88 cured. After curing, I then spanned all the bridges with 1/32 to give strength. The wing was then turned over and any protruding 1/4 ply was routered flush using the aforementioned jig.
Gotcha: The 1/32 ply in the aileron well is needed to give strength. On my first attempt, I risked not using the 1/32 ply, when routering the other side flush - one of the bridges shattered due to the vibration of the routing and lack of a solid surface.