I went up the club and had another go with the big bow, the first few shots still had me struggling, but a second try later was more successfull. I'm definitely getting it to 28" now, and even hitting the target! Thanks to Dave at the club for taking the video.
You can see on the video, I get the draw back to about where it was on the previous video, and then there's almost a pause and I work my back and shoulders to bring the right elbow back and down to get that last 2". Much more controlled, but still very hard work!
I've put the bow on the tiller and taken it to 28", it pulls 92 pounds which gives me a whisker to play with. I may take a few scrapes off the lower limb inner third as it does look a whisker stiff.
To get a more accurate weight I actually weighed the scale which hangs on the bowsting. The scale itself weighs 2 1/4 pounds, which accounts for the slight over weight. While I was at it I also re weighed my old Yew longbow, it now pulls 68# which isn't bad considering it's age and the overdraw I've subjected it to.