Has anyone used the Britax First Class with a lap belt?

[tutu100]

In the instructions for mine it says it can be used with a lap belt. Normally I don't need to do this, but when we go on holiday we are taking my Mum and space wise it would be a bit more comfortable for us if we put Ds2's seat in the middle, but obviously not if this compromises his safety at all.

Just wanted to know if anyone else uses their car seat with just the lap belt.

i use 2 seats with lap only belt and they are fine. i'm sure britax wouldn't approve it if not as safe?

I use Britax baby safe with the lap belt; the ISO kit was just too expensive