XTSL FFing

Ok, so my son will be 4 in about a month. He still fits RFing in the XTSL and I intend to keep him that way until he completely outgrows it (which I think will be by height before weight....he is currently 36 lbs and 41 inches tall). But I am still thinking ahead for when I will turn him, which I think could be a few months down the road or maybe longer, depending on his growth.

So I was wondering.....how do people like this seat FFing? He uses a FFing RN65 in my mom's car and it's okay (although that chest clip is HUGE and bulky compared to the later model ones).....he is on the top slots, but probably could be on the second to top.....several inches of growth FFing. But the XTSL headwings seem to slip down a lot (although I think it might be from him using them as leverage when he climbs in and out of the seat).

I am debating buying the XTSL a new cover and a new harness (chocolate ice cream drippings on the current harness and the cover has never been taken off.....we've had the seat for a couple of years, so I know it could use a good washing). But I don't want to drop 80-some bucks on a new cover and harness if I am not going to like the seat FFing since time is limited.

I keep going back and forth between just using the XTSL until he outgrows in completely and then going straight to booster around 6ish (assuming he makes it that long FFing in that seat) or just buying a Frontier when he goes FFing and not bothering with it FFing at all.

Thoughts?

I like the seat as a FF seat. I have a 48" tall 5 year old riding in one in my car. Call or email SK if you're having trouble with the head rest slipping down. I had that problem with one of mine, and it turns out it wasn't slipping at all; it had extra EPS foam that covered the slots when it was in the top position. What I thought was the top position, which was the only way I could access the top slots, was actually above the top position, and it would settle back down into the top notch with use. They sent me new head wings. Now they've redesigned the head wings slightly to make it even less of a problem (I have two XTSLs, one with the older head wings and one with newer). You may be having the same or a different problem, but SK should be able to help you solve it either way.

I love the seat overall. My son is 4 and does everything himself. He won't fit RF anymore though.

Now, I have to use SL b/c seatbelt install wasn't great. Just depends on the vehicle. I do notice the straps rub on his neck. I have them a bit high perhaps.
I just don't want to change seats b/c I like the steel frame and headwings. When he's too tall we'll go with the Frontier.

I have the XT and have only used it FF twice, but I'm concerned about the harness being hard to adjust. I felt like it was dragging/sticking against the vehicle seat.

I'll play with it more once DS is big enough to FF all the time, and I think it may he the seating position (back seat center has a bump).

Oh, and I cannot adjust the harness. That's big. Oops.
BUT he is in a tshirt every day now so I can just keep it tight always.

(You can adjust it but it's tug, tug and not easy). I am totally over that though b/c I like the sturdy frame. We just deal with it. I also bought a carseat poncho for winter.