Haaa, Let's see... I just went through this...

TMY-2, set enlarger so incident meter reads EV0 with the "flat" dome (at ISO 100)

Expose for 5 seconds...

That gives me the same amount of "light" as my sensitometer.

Now you want something middle gray I suppose, a density around say 0.60 sound good?

That graphs under Stouffer scale step 14 which is 1.98 density.

So if you expose film that much less than the full 5 seconds at EV0, you will possibly get 0.60 density when developed.

1.98 divided by 0.3 is 6.6 stops...

So somewhere about an 1/8 or 1/15 second should do the trick...