M_P -

My background ... a committed backpacker until I reached 60.  Now, I'm transitioning into more canoe travel.  (For these old bones, it is nice to spend most of my day without a pack on my back and enjoying the scenery going by.)

Generally speaking, you're going to find the conditions of portage trails to be poor compared to most hiking trails in the Rockies.  Won't be facing anything like the vertical climb to reach Sky Pond in RMNP, but I've sometimes come upon a point in the trail where my initial impression is "yeah, RIGHT!" based on a step or two I'll need to make to get over a vertical rise/fall.  More often than not the elevation change is very minor, the issue is more that the rock face is granite and if its wet, you'll have little traction.  

So, as previously mentioned, the issue really isn't the load you can carry but what you can carry safely.  While I can carry 120 lbs, I feel I can safely carry about 70 (I'll usually limit to about 60 on hikes in the Rockies).  So with that number in mind, I break up my load in such a way as not to exceed that number.  For me, that translates into double portages ... food tends to be a relatively hefty mass since all of my trips are over 10 days.  For individuals this hiking experience, you'll find that walking with a canoe overhead will feel unwieldy ... but you will get use to it.  It does make negotiating deadfall "interesting" at times.

Good new for the trip is that you don't have to suck wind because of the altitude.  The bad news is that you'll sometimes find yourself wind bound.  Also, you might want to think about what you'll do when you can't get a tent stake in the ground (it happens ... some campsites are on rock slabs which might have only an inch or two of actual dirt covering it, if that).

As far as finding portages, a couple of other things that might tip you to a location ... bent grass along the edge of the forest, an uncharacteristic gap in the trees at ground level, exposed roots that show a bit of scuff, rocks with unnatural markings, unusual colors on slightly submerged rocks (gel coat residue).  But, my experience is that if you are patient and do a little searching, the portage will "show up."

dd