I'm 6'1" and have reasonably long legs. On the Zeplin, the footplate is pretty much half way on it's adjustment, so it can take a lot bigger guy than me.
Mine is the smaller seat and it's a snug fit (105kg)but certainly not uncomfortable. There is quite a bit of ski between the inside of the seat and the outside of the ski. It's a bit hard to measure as it slopes down towards the water. Comparing it to the bucket on the V10 which is only about 15mm between the inside of the seat and the outside of the ski. The V10 sport is somewhere in between. I find all 3 seats quite comfortable, but the V10 is definitely the narrowest.
As to vertical(ness) of the seat, I'm asuming you're asking about the sides (hips) of the seat. I find it very similar to he V10sport, but pretty sure I'm comparing it to the wide seat version of the V10s.
I haven't sat in the small seat version of the V10sport but if it's anything like the V10L (for small people) I find that too narrow and my nuts get squashed between my thighs.
The wide seat option on the Zeplin must be huge and as it is also placed further aft than mine, it would take a really big guy to not fit.
The seat on the Zelin is also not as deep as the Epics, so remounting is pretty easy
