without some very good weather and a tailwind, the trench is not possible without carrying extra fuel.
Weather should be good that time of year, but you can get yourself into some nasty situations due to reporting points being so far apart you go beyond point of no return before you find bad weather.
Yak to penticton should not be difficult to do. If you need to stop before penticton, stop in Orville for fuel, (follow the big river up from Yak, and then keep going north when it bends east- up the valley). If you stop in Orville, skip penticton and head for Kamloops to check with customs and fuel up.
Williams lake is the next stop.
Prince George, (Quesnel if you get tired) or Vanderhoof.
If weather is good, head west to Smithers.
Now you have some decisions to make. Terrace has fuel I believe, so if you decide to head out the Skeena tank up at Terrace!!! You will have an hour or so down river to Prince Rupert, then about 1.5 hours to Ketchikan OVER WATER. plenty of land, but lots of water crossings, so do only with nice weather.
If the coast is not clear, (pardon the pun), you now need that extra fuel probably. Fly north out of Smithers up the Casiar. You can land at Bobquin and fuel up from your tanks. Now you can either head down river to Wrangell and check in with customs, or you can continue north up the highway to Dease Lake for fuel.
From Dease Lake Jacek has the route for you: north west to the inklin, then follow the water down and out!
The places you will need to be cautious:
Smithers to Dease Lake long stretch with little wx and fewer fuel stops.
Terrace to Ketchikan- no fuel in Rupert!!!!
Wrangell to Juneau- Petersburg might not have fuel.
If the coast wx is bad, from Prince George follow the higway to Ft. St. John, then Ft. Nelson-Watson Lake-Atlin and over the mountains to Juneau. Or from WL go to Whitehorse and check with Customs in Skagway. Sometimes they will check you in in Haines, but you need to call them ahead and ask.
You moving to Juneau or delivering?
Call me if you want to talk the route. It is not as hard as it sounds. I took a cub down in november last year, 36 gallons, and did fine even with snow and ice.