Wow, 18lbs is a lot. My herd has some checkered giants in their heritage but max out at abot 10-11lbs now. My first permanent house bunny, Herr Hase, had quite some of the features, like the longish slender build with rather strong bones. Great character.
I also like that I don't easily step on them and that they are safe from cats
We had a rescue from a shelter many years ago listed as an English Spot mix--several months later she tripled in size and was just shy of 21 pounds--largest bunny we ever were blessed to live with--a real sweetie, and HUGE! Now all you need is Perdita.