The only issue I can see is torsional flex under load might become an issue. I have seen That be a with this type of structure under loads that where not along their axis (which the Z plate and the resistance to cutting will not be at all times (other times it will be). As far as weight moving up to a 2:1 reduction in the pulley system you are going to using should more then take care of any mass issues. Also depending on what screws you use that can become a non issue rather quickly. Truss designs are fun to work with as I have helped build more then a few and done properly they can be extremely strong.

Michael