Recreational & Family - Burley d'Lite - Which Models are Too Old?

I have an older Burley d'Lite trailer, the kind in the attached photo, which I picked up second hand. The "V" strap wasn't doing a good job of holding the little one, so I bought the upgraded seat from Burley. That helped, but I still had issues with the seat back pushing on his helmet and making his head lean forward. I put a foam pad behind him to scoot him forward to get around this problem, but then he doesn't have much of him sitting on the seat and I suspect that may not be comfortable.

Other than that it's a fine trailer. I would like to upgrade the trailer to a newer d'Lite, but I'l still like to buy used. I understand the newer d'Lites have a recessed helmet pocket. So how old of a d'Lite (or a Burley Solo) can I get that will still have this feature?

Any reason to stick with the Burley brand? There are numerous other fine trailers out there that could fit your needs. Although I think based on volume you are more likely to find a used Burley.

I wish I could tell you a particular item or description to look for to determine if the helmet pocket was there, but I do not know.

I have a bunch of these (http://www.wicycle.com/hitchandpin_small.jpg) on all my bikes, which are compatible with the Burley alternate hitch. So I'd hate to have to revisit the mounting issue.

If it has purple anodized parts and biopace, then that Burley might be too old.