new frame has a slightly longer length chain stay than when i converted my last one.

The parts I have are 36/21 giving me a 1.714 ratio. Adjusting the chain uses a large proportion of the adjustment in the dropouts. Calcs say it gives a ctr to ctr of 17.35" (there's stretch too) which puts it a long way back in the adjustment,

If I change the ring/cog I can get to 32/19 giving a 1.68 ratio and a 17.095" stay.

Question is, before I spend a whole 30 quid on parts... Will I actually notice either difference.

My gut says I wont notice the change in ratio too much as its only the equivalent of just over half a tooth.
I think the shorter chainstay might work well though...

Probably dosent matter a jot either way, but what else would I spend my time thinking about on a Sunday night... :?

If you think 1/4" difference in chainstay length will be noticeable, go for it.

Personally, on my last 3 singlespeed frames I've had,
I've never noticed it. As the chain stretches, I simply extended the wheel back to tension the chain and have yet to notice the minor difference

My gut says I wont notice the change in ratio too much as its only the equivalent of just over half a tooth.
I think the shorter chainstay might work well though...

In reality I think most of us can ride any old pile of flexy, wobbly, bent poor show and not notice ... but 6mm on the chainstays could be a serious matter

serious indeed... :D

(I could do with a new chaining before too long anyway so was wanting to do a proper job)