I have the following geo for my Leeson:
Cstays – 380mm - this is standard on Ashton, Leeson and Curtis so is pretty much dialled
Wheelbase – 1030mm
Headangle – 74 degrees - an inch tighter than the Ashton and Curtis Standard, make the steering a bit quicker and also makes the bike better on the the front wheel.
BB - +25mm – a bit of bb rise is good to give extra clearance, due to the smaller wheels. Make sure you put a extra 25mm of spacer on your headtube to compensate for the bb rise. The leeson comes with a 120mm steerer tube, which makes the bike look a bit cleaner as you don’t have to put as many spacers in.
I had a go on a 1000 wb leeson at the weekend and it was uber spinny and flicky, but it was still decent on the back wheel, the guy that rides it though is around 5’7’’ and you are quite tall so maybe something around 1020 with a 73 degree headangle will be good of park stuff.
I haven’t watch your vid yet, will do later.and make any new comments that my or may not arise.
mike