The filling in on the gussets is a bit slow going, but this is after 2 or three layers (can't put it in too thick or it will not dry properly and crack, so I have been building it up and sanding it smooth after each layer).
This is the toptube - downtube - headtube intersection:
I think that will be good for primer after one more layer of bondo probably. You'll notice some aluminium peeking through around the cable routing inlet on the DT - I ground this down quite a bit, but I didn't want to push it too much as the walls of the actual tubing here are incredibly thin, and I also am not sure if it the chunk of aluminium would have been welded on top of the tubing or into a hole in the tubing... In any case, a slight bulge in this area smoothed out with the filler won't make a difference, especially as it merges into the aero profiling from the head tube.
The downtube-seattube intersection will likely need a few more layers of filler:
this one is a bit messy around the area where the front derailleur hanger was (on the ST), and there is quite a bit of smoothing to do between the DT, ST, BB shell and chainstays. Also the gusset comes right up to the tapped hole for the bottle holder, so I am not sure whether to bring the gusset down a bit so it ends smoothly before that, or just go right over it. Since this is meant to be a tarck bike, and not HHSTTB, bottle cage is kind of out of place anyways #amiright?