We have been touring with camping gear, etc., for 35 yrs 200K miles, with front/rear panniers on the bike. Agreeing with Ross200, frame considerations are foremost with equal attention to wheels. Some bike makers have eliminated the diagonal bar and have argued that increased tube diameters compensate. Perhaps, but we are very suspicious of this claim. The dimensional stability a diagonal tube provides cannot be easily compensated by larger diameter tubing. Over the years we have meet many tandem riders that have had problems with frame flex which was exasperated with gear. Their solution was a trailer, but a tandem w/o trailer already poses maneuvering problems. While santana is not very innovative these days, santana's huge mark on the tandem world in the late 70's was a stiff frame with a diagonal tube. Our first tandem was a stiff santana noventa and it has hauled much gear without frame flex (even while standing on pedals). Our 2nd tandem (R&E) is custom and has a long stoker compartment with a diagonal tube, again very stiff. We are taller and with bike/gear about 470 pounds, and it hauls all of our gear without a problem. I would not risk the purchase of some other frame design with such weight.