I've done 7 or 8 solo BW trips.  I triple portaged on one of the first ones, when I was carrying 90+ lbs.  Since then I've trimmed the load to about 85 lbs, and that includes a chair.

Double portaging, on the first trip I carry the boat and the small pack, 20-25 lbs.  With a heavier boat, say, 55 lbs, I'd take the day pack instead.  With a lighter boat, say, 40 lbs, it's much easier.

On the second trip I carry one large pack of about 50 lbs and my 10-12 lb daypack.  The daypack goes in front where it helps counterbalance the weight behind.

The boat comes across first so that when I arrive on the second trip I can put the boat in the water and drop the pack in without having to pick it up a second time.  It saves wear and tear on this 66-year-old body.

More info and pictures of loaded and unloaded boats on my website,   (You need to Login or Register.