Utility Cycling - New Xtracycle donor frame?

So, I've had my X for going on two years. I use it a lot, and it's really handy, but what drives me crazy is that it's so flexy/noodly. I compensate pretty naturally while I ride, but I notice it a lot pushing it while loaded -- the bike oscillates so much from front to rear, that it wants to lurch out of my hands. It does affect my riding, too... makes it a little less enjoyable and controlled than I would like. I regularly carry passengers, heavy loads, etc. -- nothing too crazy, but often >150 lbs.

When I built the bike up, I used a nice old Interloc cross-country frame. It's a very light, racing-oriented frame made of Reynolds 853 -- probably just over four lbs. I think I had the exact wrong idea; the qualities that make a nice mountain bike (flexy, lightweight steel) seem to cause some ride problems in the cargo world.

So, I'm thinking about trying to find a really beefy aluminum frame, one meant for real Clydesdales, on the supposition that those frames were meant to stay rigid under greater than normal loads. I've been looking at something like the Kona Hoss -- used Hoss frames sometimes show up on eBay for $100-150. Any other suggestions for super beefy mountain bike frames (that don't have crazy dirt jumper geometry)? I don't want to drop crazy money on a Big Dummy -- just want a nice, beat-up old frame to stiffen up my current ride.

you will pretty much find this regardless of frame and fork combo.

the best solution of course is The Dummy

and even at that... the Xtracycle FreeLoaders have a tendency to flex.
so i use the WideLoaders a lot, and focus the weight to be cinched down and into the lower part of The Dummy, rather than hanging the weight from the V-Racks
http://forums.mtbr.com/showthread.php?p=5611898&posted=1#post5611898

if you were absolute on using an Xtra Convert Job
I'd pick something like a Surly Instigator, and the fork to match.

I built my longbike up with an old Norco Kokanee mtb frame that is straight gauge chromo as I knew the bike was going to be subjected to some serious loads... I have carried as much as 200 pounds of gear on the bike and had nary a problem.

For a bike like this and the use it is subjected to using a lightweight frame or aluminium made no sense.

if you were absolute on using an Xtra Convert Job
I'd pick something like a Surly Instigator, and the fork to match.

+1...:thumb:

I guess I really just balk at the price of the Big Dummy -- that seems like way too much for a TIGged straight gauge 4130 frameset, even one with an extra two feet of rear triangle. I'm sure it would do the job admirably, and I'd consider it if it landed around $650.

I hear you about the Freeloader automatically adding a certain amount of flex. I think my choice of donor frame is adding to the problem, though. I can actually see a harmonic wave roll up and down the bike if I shake it by the stoker bars!

Upgrading to a truly massive, high-trail front fork (Kona P2 Jump Fork) really helped with the shimmy/speed wobble problem I was having -- it tracks reasonably well pedalling with no hands now. It's a ~3-4 lb. cro-mo monster of a fork, with legs at least half an inch thicker than my regular P2 fork. I think I need the same kind of "upgrade" with the frame -- and I only suggest aluminum because the stiffest bikes I've ridden have been aluminum. I would be open to some massively overbuilt 8 lb. 4130 frame, too!