The protecta harness is what we have Vic. I bought the Boston Hipod, which I thought was a great bargain at only $129 or something and has the highest safety rating on the good old CREP website. And it says, in all their books and stuff, that you must use an additional harness. So I bought the protecta as well - and it's like $90. Not cheap. And now I find it's unsafe. Grr!

I need to look at the manual and see again what it says about the harness...
It is only actually unsafe if used incorrectly (but the chance of using it incorrectly would be pretty high for me)

This is the response I got from Britax

"Hi Victoria, our research shows when the harness is used in conjunction with the lap sash belt it maximises the upper torso support as long as this is fitted each time using the manufacturers instructions. It can also prevent a child from falling out of the sash belt whilst they are sleeping, slumping or wriggling. Without torso support your child is at risk of being flung forward in a crash which can cause serious head, abdominal and spinal injuries"
The bit in bold being key, I personally would rather after seeing the other evidence go with just the lap/sash belt on a booster because I would not be confident with fitting each time using manufacturers instructions. The above also puts me off Britax a little because they have not referred to the other evidence at all. I prefer the Infa approach of not recommending the harnesses unless have only lap belt.