Well, I do dayhikes with my Gowland 8x10" and usually around 5 or 6 lenses and three filmholders, or more holders if I'm working out of a car. I have a 12" Dagor and 19" Artar in barrel with an adapter to use them on the Ilex 5 shutter of my 10" WF Ektar, and then I have a few small wide lenses that cover 8x10". The whole thing fits with all the usual accessories in a knapsack of the sort used for laptop computers and the tripod hangs from my shoulder on a strap.

If you want to go really small and light, look for one of the old casket sets (the premium ones are the Busch Vademecum set and I've seen uncoated Dagor casket sets), or if you have the budget for the new Cooke lens but want more options, consider the Wisner casket set:

http://www.wisner.com/Page15.html

My superlight 4x5" kit is a Gowland Front Moves 4x5" with a Symmar 135/235 convertible, 90mm Angulon, Linhof 42mm shade and filter kit, Gossen Digisix meter, and as many Grafmatics as I need/have room for. Just scale up to a 300/500 Symmar, 210mm Angulon and an 8x10" Gowland or Toho for a comparable 8x10" kit.