In reply to bouldery bits:
I used the Orge 33 for a bit. It’s a great design but ME used a cheap foam in the shoulder straps which snapped after not much. I returned it to the shop where I purchased for a refund. The Tupilak packs use better foam, but they’re much more expensive.
I would echo what others have said that a light mountaineering sack might not be the best option for doing your ML. I used a 30 litre days sack on the first couple of days, and a 50 litre sack for the exped. Some folk will use smaller bags, and some will literally carry the kitchen sink. I’d aim to go lightish, particularly on assessment, as otherwise you’ll get unnecessarily tired. That said if it’s unseasonably cold or wet, it’s worth going a bit heavier, in terms of waterproof clothing, warm stuff, and food.
I would also recommend not going too small. Sure you can get everything for 2-3 days into a 25 lite sack, that you carefully packed in a warm living room. Re packing that bag when it’s 5 degree, windy and raining, isn’t gonna be much fun. Also what happens if someone in your group is tired/injured and you need to carry some of their kit.
I would use whatever sack you have already for the day walking part of the assessment/training, and get a 50 litre bag with a removable/extendable lid for the expedition. You should be able to get everything into that no problems.
The Alpkit Ibex is a great sack (very similar to the classic Pod black ice). I used one on the exped on my a Guides’ winter test, and it was great. Another good option is an Aiguille Alpine Zyphr. These sort of sacks are great all rounders and are perfect for days out sea cliff climbing, where you need to cart around big racks, absiel ropes, and a big packed lunch.
https://eu.alpkit.com/products/ibex
https://www.aiguillealpine.co.uk/product/rucksacks-bags/climbing-alpineruck...
Good luck with the ML. You’ll have a blast.
Tom