I was thinking of using the 4X5 for landscape photography to get started, so portability would be a major concern. This is why I was thinking a well constructed field camera might be a good choice. I purchased my berlebach to support a 90mm refractor weighing aprox. 9 lbs, and I believe the berleback is rated for loads up to 100 lbs. which means just the tripod alone is gonna be a load. Although, I do have a manfrotto 055XPROB that can handle 15-16 lbs. which could be an alternative.
I'll look at the Sinar and Toho. Thanks for the suggestions.