I compared the Aliner, with dormers, to the Flagstaff and they are a nice option I wish FR would offer. The one above the Aliner's dinette added a nice amount of space and made the trailer "feel" bigger than the dormer added.
Even without the FR's power lift, on some models, the Aliner's roof didn't feel heavy as most of the dormers weight is at the hinged end. But they do add about 60-70 pounds to the roof weight each
. The front and sides are cloth, Aliner only did "hard dormers" on a few models and no longer offers them. I saw a used one with the "hard dormers" and I'd would rather have the cloth.
The dormer adds much more usable space than FR's "bubbles", even when closed, about 4-6 inches I'd guess. Open you just added a couple of feet! As long as the cloth sides and front is tucked in properly they do not impinge on space when not
being used. Setup is as simple as releasing a couple buckles and pushing up a couple of corner poles to lock them in place. All the parts are hard mounted so nothing can get "lost".
The downside? Well, first FR doesn't offer them. Second, each
dormer adds around $900 to the Aliner's cost.
Even at around $1K each if FR offered them I would have ordered a front dormer on our T21QBHW. The added space flexibility would be nice to have....