It is likely marginal but a lot depends on additional information. One piece is what do you expect to machine The second is how high are you in Z. Perhaps most important is what are your expectations out of this machine.
As for the angle iron if you do have a problem I wouldn’t try to correct it this way. Most likely I would just buy another beam of larger cross section. In any event I wouldn’t stress over it until you have considered how the machine will be used. I can see a machine with such a gantry beam as being usable in a number of circumstances. However if your goal is to push the machine hard in difficult materials and at the same time expect high quality you likely will not be happy.