Can't re-thread strap on Intera (help!)

[AutumnMama]

I took all the straps out of my Intera because I was going to use it as a temporary booster for DD. Well now I need it for DS2, so I have all the straps back in except for the one that attaches to the back and goes under and then through the bottom front.
The one where you adjust the strap tightness.

That strap had actually been recalled last year, and they sent me a replacement.
I can't seem to find the instructions from the replacement strap, but I recall it being fairly tricky to get threaded back in...involving some very sticky tape and a dummy strap or something (yeah, shouldn't have taken that one out I'm realizing).

Anyway, I can't download an instruction manual from Safety 1st's website, and the phone lines are closed.

I can install his SafeSeat, but I'm ridiculously close to being able to get this one in, and I'd rather not mess with 20+ extra minutes of a center install in a small car (I'm pg too) *sigh*

So, anybody have any ideas for me? :o

[tiggercat]

Try threading something else that is thinner and stiffer (pipe cleaner? piece of strong paper), and once you have that through you can tape the end of the strap to it. I did manage to get one through without a guide (parents had done exactly what you did, converted to a booster and then couldn't get it back together for a littler one), but it did involve much cursing under my breath.