[Mgs] Importance of 3 screws in float chamber lid

[Simon Matthews]

On starting to look at over-revving issues, I noticed that one of the float
chambers has 2 screws in the lid. On removal, the reason becomes obvious:
the remains of a screw stuck in the threads.

So, my question is: how important is it to attempt to remove the shank of
the screw and put in a new screw? If I mess up the removal, I might damage
the float chamber, which then apparently means a new carburettor (Moss
doesn't show the float chamber as a separate item). So I am wondering about
re-assembling with only 2 screws.

Simon