I own a 2017 Nismo V2, a V1 may have a different dimension.
It'll be difficult to measure it accurately, but I'll have a go on the weekend. I'm no spring chicken and I don't have any back issues, but I find it more difficult to get out of, than fall into! Actually, difficult is the wrong word - I'd say awkward and needs just a tiny bit of thought!
If I've not responded by the end of this weekend, give me a reminder here.