Originally Posted by
OrangeBike
Tell you what, I will take a picture of it with the two links (out and inner) back in and see what everybody says.
If that's too loose and this is too tight, then dddd's suggestion of moving the derailleur forward a scootch is the way to go.
With a modern chain, You'll need to add a second PowerLink in order to lengthen the chain. Re-riveting modern derailer chain usually results in an extremely weakened sideplate retention at the affected pin.
I wouldn't place two PowerLinks next to each other, since their tolerances are measurably different from the rest of the links. What I do in such instance is to splice in a typical remnant piece of perhaps 6-10 links, so that the two PowerLinks are not so close to each other.
For your test purposes, you can simply engage the two ends of your chain with the chainring, leaving a 2-link gap that is toward the front of the bicycle. The free ends can be held in place with nothing more than a loop of wire, string or a twist-tie and will not fall out of place on the chainring unless the chainring is rotated.
You'll have to do all of your "shifting" by hand, moving the thankfully-clean chain to the cogs/rings that are to be evaluated for chain "tension".
But doing it your way (with a re-installed pair of links) is also fine, for testing, just not for any serious riding to follow.