Actually, the Radian is the only seat that you can use the tray table with, because it's such a low profile.
I have pics if you want but they're rear-facing, since my son was only 29 mos when we flew w/ it.... I loved the Radian for flying, we had used a Marathon before that, the Radian was much easier. It's heavy...but if you're taking it anyway, might as well use it - that way you KNOW how it's handled and that you have it with you. No worries about it being thrown or dropped and damaged. We brought our stroller just to carry the carseat and bags. =)
The one problem that I did have w/ the Radian FF (we RF'ed on 3 out of 4 legs of travel, the 4th we were in a seat that it wouldn't fit RF'ing) is that the buckle ends up behind the kids back. Tried using an extender and the same thing. There is a plastic piece on the back of the cover over the belt path...but DS still complained about that. Maybe someone here will have better suggestions as to what to do about that, if there's anything? I ended up putting my sweater behind the cover over the belt for extra padding.
Here's my pics: (sorry I don't have an FF)
(yep, the straps are too high, had set it for FF since we assumed it wouldn't fit RF...DH installed w/out changing the straps during the "preboard" and I didn't feel it was important to uninstall, change, and reinstall while everyone waited for us, on the plane.)