I don’t like the Dome Hill route, Bolts. You would be cutting off too much of the nice part of the river. We found it negotiable (but small) from fairly high up, and that would tempt me to consider the High Dome option. It will be satisfying to complete, and hard work is, after all, only hard work.
A quick search of my own posting history on this forum found the passage below from 2008. Although written for Duke (Eliam H.) who was considering the eastern approach, it may be of interest:
"I did the Murchison just with my wife, about 15 years ago (approx 1993). It’s a great paddle, but it’s a job to get in and a job to get out! I doubt it’s been done very often in the last 15 years, so you should find it quite pristine.
We dropped in from the saddle between Horizontal Hill and the Guardians. You can approach from either direction, there is slightly more scrub from the Horizontal Hill side, but more climbing if you go over The Guardians as we did. Having previously done the full Gould/Guardians/Horizontal circuit, we chose the higher route because we knew it’s a nice walk. You go virtually all the way to the end of the Guardians (via Gould Plateau) and then there’s an improbable-looking descent down the crags to the left, (to the south) that brings you nicely down to the boulder-field in the Horizontal-Guardians saddle. You bash on down through nice myrtle forest to the valley floor; I recall a bit of Horizontal scrub in the bottom. It’s a U-shaped ex-glacial valley up there, so it’s a bit flat across to the river, and the flat bit is where the scrub is slightly annoying for an hour or so. When you get to the river, it’s almost big enough, just wade downstream a short distance and you can get in. We spent a couple of beautiful days on very easy bouncy water; there’s a great sense of remoteness and it is generally a delightful paddle. You could bag Mt. Nereus on the way (doing it over Macs Mt. from the Labyrinth is a drag.) Canning Peak would also be a nice bag. When you get down to the Bluff River, I suggest you camp prior to pushing across Lake Murchison. You can explore upstream in the Bluff River; it looks a really nice stream. Once you turn the corner onto the flat water of the Murchison Impoundment you really need to keep plugging away at it until you reach the access road at the far end. For us it was a hard day. I ended up towing my wife a lot of the way into strong headwinds. We found very few opportunities to beach for a break on Lake Murchison. For lunch we bobbed about in the middle of the lake for fear of puncturing on the dead sticks at each side. I scrambled onto the branch of a submerged tree to access my rucsac for food. Eventually we reached the end of the lake with tired arms at dusk on New Year’s Eve. We were 5.5 days from Cynthia Bay to Tullah using older heavier equipment with fixed paddles in the scrub. You should probably expect 5 days all-up but obviously have a little spare food for unforseens."
Incidentally, the traverse from Eldon Peak to Eldon Bluff is sensational. You will have a great adventure, and I like the scope of your project. Great to see other Tasmanians gearing up for this kind of trip, as I know Van D. and his friends are also doing.