[rdmarsh]

2186 has been using their 1-inch profile (10-series, I think?) since 2008, and the only problems we've had with it have been related to ship times. It seems to be the best off-the-shelf material running around that doesn't need welding or other advanced techniques. One thing to note is that the cost is tilted heavily towards the fasteners, compared to the breakdown for other materials.

As far as buying it, they have distributors that you are supposed to order from. 80/20 offers a steep discount to FIRST teams, so you should make sure that your distributor is using that. The t-slot nuts, brackets, plates, etc. you probably want to order from the same place that you get the extrusion from, but any hardware store should have the bolts. You should order the generic fastener parts (90 degree gussets, 2-hole strips, 5-hole angle plates) at the same time as the extrusion, but leave the weirder brackets for a separate order. I'd recommend ordering as many of the slide-in nuts as you can; there's nothing worse than losing a week of build season waiting on them, and you always underestimate how many you need. If you get more than you need this year, it just means you've got more to make for the ones you'll lose. The drop-in nuts are also really important. They're kinda pricy, but way better than taking apart the frame to add a single slider.

I wouldn't plan on mixing thread types. They'll probably fit, but are likely to cause more wear than using appropriately matched nuts and bolts. In an emergency, it would be better than nothing.