I actually had a friend make me some side water bottle holsters - similar to the ones that HMG now sells, but full dyneema gridstop. Sorry - no direct experience with the HMG ones. I used a prototype front pocket made by HMG which worked (works) really well to add some additional volume.
Based on your load requirements, the Trance would be overkill. The Porter packs are tall and lean beasts, which is what makes them multi-sport packs, in my opinion. They also compress really well.
If HMG is what you want, I would go for a Porter - it is designed a little differently than the Windrider series and carried better for me. The Windrider carries well, but the Porter carries better (belt design is a little different, at least was when I used both packs - newer versions may be more alike).
What size? Probably the 3400, which would give you the best overall compromise (I can do 6-8 days out of it). If you plan on doing shorter trips and would require even less volume, then maybe the 2400 with the front pocket, which is removable so the pack becomes a little more modular. I can get 3-4 days out of the 2400, assuming the weather is not too cold which would require more insulative layers.