I'm going to be swapping a Costar stab for a Cherry platemount stab soon. Opposite of what you're looking for... AFAIK, on the Poker plate (if it's The_Beast plate) needed to be sanded down to fit the stabs in. And does the bar need to run under the plate? I thought so, thanks lysol.
I've done this exact swap. Ivan is correct, assembly order is critical. I did
not need to sand my Beast plate, however.
#1 Assemble stabilizer pair, including cross-wire. Orientation of both plastic pieces is important. Left and right are identical. Make sure you snap the wire into place at both ends. The crosses should fall in and out when you turn the assembly over.
#2 Install the stabilizer assembly, first the tails of the plastic parts, then pushing the wire through the slot, then clicking the snap-on tabs into place. As before, the crosses should fall in and out when you turn the assembly over.
#3 Install the switch into the plate.
#4 Attach a spacebar, discover you've gotten one or both of the stabilizer mounts wrong and start over at step 1. Repeat until it works normally.
#5 Complete keyboard assembly, including soldering.
I can confirm that it is
possible to install from underneath. I can also confirm that you would
never want to do that without some overwhelming reason.
I cannot imagine how you could install the stabilizer with the switch soldered in place, especially with a PCB firmly attached under there. If I had to do that, I would:
a) De-solder just that one switch.
b) Remove the switch from the top side of the plate.
c) Install the stabilzer assembly as shown above.
d) Install the switch.
e) Physically test everything very thoroughly.
f) Re-solder the switch.
And that would absolutely not be possible without the slot for the stab wire.
FYI, Mouser sells these for 2x switches, and they are identical except for the length of the wire. Plan on getting some spares. Thise tiny plastic tabs snap off very easily!
Good luck!
- Ron | samwisekoi