John: thanks for the comments - from a ratio perspective I too dislike the 13-17 jump but was trying to avoid buying yet another cog for the uniglide cassette.....and since I rarely if ever use top gear I was not so worried.....but you have opened up another possibility - I had not considered the 7 speed cluster so I will look at that. Is that cassette compatible with the 600EX hub (circa 1980?).

I have a 38T front ring on the way now....I will try that with the standard rear cluster first, and I have a 27 tooth Uniglide cog on its way as well to experiment with.

Road Fan: you pointed out something I had missed - I was keeping the 13T small as it is the lock ring, but just realized after your post that eliminating the 15T second cog (I was attempting to shift everything down by one to make room for the 27T low gear) may not be possible as the 17T can't go in the second position on the uniglide freehub....Perhaps I just need to spring for the 15T lock ring for the first position and keep the original progression, eliminating the 13T and adding the 27....

Regarding the RD: I have a mint SunTour V-GT Luxe to use if necessary,though I was trying to keep to the all arabesque group for looks.....

Finally - my original question was "what happens if I exceed the rated chain wrap by 2 teeth"? I think the answer I got is possible chain sag in the 13/38 combination - is that the only impact? Or do I need to get the Suntour ready to mount?

And just in case there is any doubt - I am doing this as a learning experience, so please keep the suggestions coming - I am not set on any particular direction and the bike is quite enjoyable with the stock gearing.....just wanted to play around to see the results in the "real" world.