D/G units blown

[Robbox]

I'd like some glazing advice here. We have cottage windows with small panes of d/g units. They are held in place by mitred beads. The problem I have encountered is that the pins that hold the beads on the centre partition of the frame have to be nailed in so carefully otherwise you chip a unit and eventually it blows.
So are there any double sided adhesive strips I could use that do the same job without pins?
The other question is I need to replace the beads, what is the best way to achieve accurate mitres without a chop saw?

 

[big-all]

the secerate is the hammer slides down the glass
or a bit off smooth rigid plastic on the glass never breaking contact so cant impact the glass