There's no real benefit for giving the actual stuffsac measurement as the bag will compress further and it's always best to leave the bag 'soft' when packing anyway so it is easier to stuff into the space available in your pack.
I see illegal off roading in the Hope Valley 2 or 3 times every week - often the same small group of motor bike riders. The fact they are there doesn't bother me too much as what they are riding on is used by hundreds of walkers, runners and mountainbikers (as well as farm traffic) every week.
What does bother me is their complete lack of skill, knowledge or ability to ride a bike properly. A great one I saw recently was 2 guys on big trail bikes trying to ride up 'the beast' (the bridleway that runs from Hope Cross down to the reservoirs/A57) I sat and watched (and laughed outloud) as both riders continually stalled and watched as their bikes tried to bury themselves in holes of their own making before the front end came up and dropped these 2 'off-roaders' on their arses.
They tend to be a friendly (if not that bright) bunch and I don't tend to point out that they shouldn't be where they are anymore because I honestly don't think they know where they are anyway.
I'm not sure where I'm now going with this one - perhaps i should spend more time conversing with real people than out on the hills... anyway .... illegal off-roading happens every day in Derbyshire and it always will, I don't mind the noise or smell - the 1000's of 'walkers' that drive 3 hours each way on a saturday to do a 2 hour walk produce far more - and, as i've said the majority of 'off-roaders' are non-hostile and generally lazy so aren't a problem - i guess I just don't want them getting in the way and slowing me down when I'm out on my bike...
Is the primaloft not just an overlay to protect the down - like the Rab Summit jacket has been on the shouldersfor a few years? I can't see why the primaloft is a problem - as there is down fill underneath it? it would probably even make these areas more water-resistant.
For what it's worth I have regualrly used a Micro baffled down jacket under a pack for the last 3 years and had no problem at all with cold spots or damage to fabrics or fill. (pertex microlight outer and 750+fill)