Originally Posted by
dddd
Is the OP aware of how the hi-limit screw functions, and of cable tension adjustment?
"cable tension " is not relevant in this case, since it's vintage non-indexing.
OP, you could try letting out the High limit screw a bit more, even though it will be a tiny bit too much when on the small ring, but riding small-small is not that common, and even still, it may be fine.