You share my concern with the lengths of tents, although I am shorter than you (at a mere 188 cm). 220 cm, which seems to be the most often mentioned floor length for Roger's tent, is conveniently also the floor length of most of the Hilleberg line. So if you can find one of those on display, it may be useful to you.
For me, the Kaitum (vertical ends, both protected by vestibules, like Roger's design) is significantly longer than I need even after snowfall, whereas their Nallo/Nammatj/Anjan (also 220 cm floor length, with one vertical end and one sloping end) are too short even without snow when I'm sleeping on my back (side sleepers may be shorter), even without a 7-cm air pad. Perhaps you can find a store that sells Hilleberg and see whether you can use the Kaitum as a mock-up of Roger's tent.
Note, however, that the Kaitum 2 has a floor width of 140 cm, although it slopes only inward from there, not outward like Roger's. So I'm not sure how different Roger's design will feel; I suspect that it'll be just fine, even if the nominal width ends up being a little narrower...
I'm very excited to see that your tent will finally be available to us less-skilled folk! Congratulations! If a large group pre-order would help keep Easton's enthusiasm up, please count me in, even sight unseen.
By the way--does it have a PU floor, or silnylon, or...? Silnylon is frustrating unless the campsite is perfectly flat--does it offer enough strength/weight/abrasion advantage to make the annoyance worth it? It seems to me that tent fabrics that absorb as little water as possible are important to keeping the effective weight down; I know silnylon absorbs a fair amount but I don't know how PU fares in this regard. I hear Cuben is pretty good... ;)