Hey Scott. I expect you'll be fine, but if not, a backpack full of gear sounds like a camera insurance claim waiting to happen. I recently had a photo shoot in Knoxville (look for it in the October Rotor & Wing, by the way) and, noting that I would be on a regional jet for part of the trip, I went to Tempe Camera and bought a relatively small Think Tank rolling case. It's not a backpack, but I didn't need a backpack (though I think they may have a combo backpack/roller).What I did need was for it to fit into the substantially smaller carry-on size of the smaller jet. Every trip before this, if I was on a regional jet, I had to plead to be allowed to keep my regular roll-on in the cabin, and all but one time I succeeded.
The small Think Tank worked like a charm and with very careful packing it carried: two Nikon D4 bodies with Really Right Stuff L-brackets, a 70-200 f2.8, a 28-70 f2.8, a 105 f2.8 micro, a Kenyon Labs KS-6 gyro with battery, extra camera batteries, extra data cards in Think Tank cases, a filter or two, some cords, a flashlight and reading glasses and air bulb and, I think, not much else. It was packed tight and, let me tell you, quite hefty. But it went right onto the regional, no hitches, and it was all I actually needed for the shoot. If I forego the gyro I can take an SB-900 flash with a little room to spare.
So, that may not be what you need or have in mind, but it's a solution of some sort...
The small Think Tank worked like a charm and with very careful packing it carried: two Nikon D4 bodies with Really Right Stuff L-brackets, a 70-200 f2.8, a 28-70 f2.8, a 105 f2.8 micro, a Kenyon Labs KS-6 gyro with battery, extra camera batteries, extra data cards in Think Tank cases, a filter or two, some cords, a flashlight and reading glasses and air bulb and, I think, not much else. It was packed tight and, let me tell you, quite hefty. But it went right onto the regional, no hitches, and it was all I actually needed for the shoot. If I forego the gyro I can take an SB-900 flash with a little room to spare.
So, that may not be what you need or have in mind, but it's a solution of some sort...