Hi Troels,
Just wanted to say I’ve built the thinwall 81’s and been evaluating for a week or so. Great. Just one pic for now. I could send more if you’re interested when I get a chance to put a decent camera on them.
Bass is very meaty. No problem there - beyond my expectations. You see in the pic the ls3/5 I built before and have used for a long time. So I’m hearing some real bass now! Of course the speaker takes much more volume and keeps composure. I was a bit bothered about slightly sibilant treble at first, but it seems to have calmed down. Possibly a mental adaptation. Not sure. I’m listening to Joe Hendersen State of the Tenor Vol 2 and the overall effect is great, atmospheric, making me tap my foot and smile… result!
Well done Troels,
All the best 
Dave Wolff

Dave,
Remember you can adjust treble level by changing R1 to e.g. 4R7.
cheers Troels