Stick with Ali profile or venture into plate?

[routercnc]

There is a spread sheet around here somewhere, I'll get back to you...

There are two here, one from Ross (#1) and one from me (#3). Mine includes the torsion calc (due to the cutting force being offset in Z from the gantry, trying to twist the gantry). You might want to consider that on top of the vertical and horizontal forces mentioned above.
http://www.mycncuk.com/forums/showth...ail-Calculator

As for cutting ali with simple tools, you can cut profile with a mitre saw with a metal cutting blade, so should be able to cut plate. Mine was a Rexon ~£100, but there are cheaper ones. Blade was a branded part at £44 - you can get cheaper but I didn't want it to let go and do me some damage.