Hey Jim, I use a Mountain Equipment Inc (MEI) backpack for 11x14. It has been with me since the 80's as my suitcase/backpack for travel but I found it works perfect for my 11x14. You can carry it like a suitcase with the straps hidden away by a zippered flap or you can use it as a backpack with heavy duty straps just like a regular back country pack. It has an internal frame and carries a load well. It also has a mini backpack that zips onto the back of the main one that is perfect for at least 4 11x14 holders (maybe more, but I don't have anymore than 4) There are numerous attachment points and d rings to attach tripods or water bottles etc. I would not use it as checked baggage with my camera in it however
regards
Erik