One thing is that different regional sections tend to have their own policy on whether or not they lock their cabins, i.e., all Bergen Turlag self-service huts are unlocked while all the Oslo ones are generally locked. So just get in touch with the regional DNT branch where you are thinking of going and they should be able to tell you. Also note that some cabins like the Oslo ones (Hardangervidda, Jotunheimen etc.) actually have periods during the year, mainly in winter, when they are closed completely, i.e., not even the DNT key will get you in.
You can use self-service huts as a non-member at a higher rate, too, but if you want to use them as backup for a tent-based trip in an area where they are locked, one of your party will have to become a member to be certain that you will be able to get in.
If you want to do Jotunheimen without the big serviced huts, then maybe March next year isn't such a bad time. Fondsbu is open and serviced, Olavsbu is self-service anyway, Skogadalsboeen, Krossbu, Gjendebu, and I assume Glitterheim (bit out of the way) all have open self-service bits. Along the southern edge there are Yksendalsbu, Tomashelleren and Slettningsbu that are all self-service. And in Breheimen everything is self-service apart from Noerstedalsseter which has an open self-service part. If the road to Sota Saeter is open, you could use that as a start point by spending the night in Bismo or Pollfoss on the 16 and take a taxi up there.
Maybe time to start planning a trip to Norway next year...
Sorry, only just saw the whole Jotunheimen discussion now, too busy with house moving and Xmas related things.
As was said before Tyinkrysset is a good option to get into Jotunheimen. Slettningsbu and then on to Fondsbu or Skogadalsboen is one option. The bus from either Oslo or Bergen gets to Tyinkrysset lunchtime-ish, so the short ski up to Slettningsbu would work well. For either Fondsbu or Slettningsbu you will have to get up to Tyin. If there is a group of you a taxi is the easiest option. There is the weasel in to Fondsbu. Otherwise it's also skiable, but a bit dull because the first 15 km are across Lake Tyin. We did that this year coming off the coach from Bergen and made it just before second sitting dinner at 8pm.
Another option could be to find somewhere to stay in Tyin, use the afternoon for a little warm up tour in the vicinity and to go to Tomashelleren the next morning. We went to both Tomashelleren and Yksendalsbu this Easter. Both self-service, slightly off the beaten path and in nice skiing terrain.
Buses to Gjendesheim, Sota Saeter and Leirvassbu only happen at Easter. A taxi from somewhere like Bismo to Sota Saeter would work. If Sota Saeter was still closed, you could always stay somewhere near the main road, go up in the morning and go straight to the next hut.
Turtagroe will still be closed, I think and I'm not sure when the weasels to Glitterheim start, nor how you'd get to the start point.
Beitostoelen could be a start point and then via Bygdin and Yksendalsbu towards Fondsbu.
That's about as much as we found out planning two Easter trips in the area
Another vote for the Macpac Pursuit. It's close fitting, stable, tough and has enough space for the stuff I need for multi-day hut ski touring.
Other packs I've used for ski touring are a Marmot Eiger which requires very minmalist packing to say the least, because it's only about 40l. It's worth using only to see the faces of the Norwegians who tend to have fairly big packs I've also used a Macpac Rimu which has a flexible, swiveling hipbelt. Not a good idea when you've only started ski touring and are still getting to grips with skiing ungroomed snow with a pack. I used it again a few years later for a May ski tour along Hallingskarvet where we camped and thus had more gear with us. At that point my skiing had improved enough that it was fine. The tour along the top of Hallingskarvet comes highly recommended, BTW. With good visibility you can see everything from Gaustatoppen to Jotunheimen.
As usual with backpacks, it'll be a matter of trying on a few and seeing what feels comfortable and stable to you. Some of the bigger Black Diamond alpine packs might also be worth a look.