I am building my Maslow after buying a metalmaslow.com kit. I wanted to modify the default frame for a 12 foot wide top with 30 inch separation but still use 2x4s for everything and change the length of as few beams as possible. I figured out that if you rearrange some pieces on the cut list all other stock lengths can stay the same. I created a new cut list and figured I would share.
Assembly instructions are same as the default. I have not yet built or tested this frame, so build at your own risk for now.