Conditions seem to be right to make 90g possible. We can only access 3/5 of the glyph of unification with a length-1 fixed arm, but we don't need access to fire or water for anything other than unification, so those reagents can be positioned permanently on the two glyph inputs we can't reach. If necessary, disposal could be layered on one of them so it doesn't get in the way while we build our product, but ordered so unification gets first dibs to the atom once the other three are in place. Similarly, we can only access 2/3 of purification with a length-1 fixed arm, but there are two options for mitigating that: a half-access bonder could allow us to pick up an iron we can't reach once it spawns from the glyph, or a half-access unbonder could allow us to "drop" a tin on the glyph input that's out of reach.

Once all that's in place, we're left with a geometry nightmare. The necessary elemental air reagent means we can't fully circle the arm as we work. At least one of the stranded water and fire reagents is going to be getting in the way as well, so even making a C shape won't save us. We can semi-permanently suppress one of the two-atom inputs so we can have four access points to work in, but making the necessary 120 and 180 degree bonds is awkward with a bonder angled to pick up iron, breaking off the necessary atoms is awkward with an unbonder angled to feed purification, and many of your atoms will only have one angle of approach to your bonder so build order is going to be very sensitive.

I suspect someone will find a way to do it, but if these notes make it to the deadline that means I couldn't.