Marathon and Wizard installs in F-250 Super Duty Ext. cab questions?

Today is my youngest dd's 4th birthday, and Gramma and Grampa decided it would be nice to take my two youngest overnight for the first time (they live over 2 hrs away). I didn't really think much ahead of time about if installing their seats would be a problem. I figured they would drive Gramma's Focus rather than the big F-250 - you know, better on gas, easier to drive, whatever. But they got here and they were driving the truck because the air is broken int he Focus. After dinner, I went out and took a look at the truck and the manual. Well, the manual said it should have tt, but it didn't (must be because it is the super duty diesel or something, maybe exempt? :scratcheshead: ). The first thing I notice is that the seat backs in the back seat are REALLY short. Other than that, I was hoping it wouldn't be too bad, a shoulder belt in each out board seat, and the lock offs on the seats should be easy right? Wrong! The back window curves in toward the interior of the truck, and if I set the seats on the seat the way they usually are, they were pressing into the back window glass, and that was before even trying to buckle in. Ugh. So, I did my best anyway. My biggest question is about how I had to install them - I had to lift the back of the bases of the seats a little and press the front of the bases down into the seat really hard to get the tops of the seats to not press into the glass. I wrestled with them for a little bit and seem to have gotten them in acceptably, but I am worried about the bases not being flat on the seat. I would say there is less than an inch between the car's seat and the bases of the car seats at the back, and it tapers down to the where its really pressed down in the front, and the seat touches a lot of the bases. It was either install them this upright, or not let them go, and dh would be furious if I said I couldn't get their seats in (he had a cow as it was that it took me over 15 minutes to get them in in the first place). I did offer to let Grampa take my van, but he didn't seem too keen on the idea. So, should I feel like they are safe in their seats the way they are? :shrug-shoulders: I'm just all flustered 'cause dh is being a pain about the whole thing, and even saying he won't watch the girls if I get in the certification class in Sept. But that is a whole 'nother post I think!
:soapbox:
TIA for any replies.

I know it's too late to change it, but the top tethers are located behind the seat back, You have to fold the back of the seat foreward, and there should be one tether in each outboard position. We have an F-350, it's hard to get at, and before I found this board I let DH not tether our nephew's seat, because it was a PITB to adjust the tether.
Unfortunately I don't know about the other issue you've had, our truck is a supercrew, so I'm not sure what you're talking about with the tapered window.