I have a 23" riser with 26lb limbs which makes them 28lb, the tiller has been adjusted to push them up to 30lb and I have been shooting fine with them and because I feel no strain or difficulty I decided to buy new limbs so that I could go up a couple of pounds. My reasoning is that I should be able to adequately reach longer distances without having to turn my sight upside down. So I bought 32lb limbs (which makes them 34lb) thinking I could adjust the tiller to bring the weight down to 32lb. In theory, this should have worked but in practise it was really hard for me to pull back. I had to adjust my clicker right out from the bow as I couldn't draw back the same amount as before. My long rod then kept loosening itself, so I bought a new one (slightly shorter) and I re-tuned my bow. After shooting a 'frostbite' with this set up and not getting very good results, I decided to put my old limbs back on. Adjusted the tiller back to where it was and then I shot a Portsmouth with a very wobbly bow. The vibration was really, really noticeable as the bow was shaking and vibrating after each shot. So the tiller got adjusted again until it wasn't too bad. Shot a couple more sessions with it and then just before Christmas it went back to being wobbly.
We now have a 'Frostbite' tomorrow. So �. I've been on the Internet looking at tiller adjustments and I found a really great PDF by Medway Archers. After reading this I'm actually thinking of buying some new limbs 28lb's which would make them 30 and then screwing the tiller right in to increase the weight to 32lb. I still have my new limbs to progress into - right :). The one thing about the PDF that I liked was how I didn't know that some limbs were already made with a heavier bottom limb so this needs to be checked first! I'm going to screw the tiller bolt all the way in and then check if the top and bottom measurements are the same and work from there. I hope it doesn't rain today as I'm going to have to paper tune again - before tomorrow.
Anyway, let's see if the shops are open!
ps another couple of great tuning guides
This is a great guide for beginners Bowmen of Overdale
Conversation about tiller adjustment
and of course the FITA Coach Manual