Guys, what about IPN? not good to use it ? i can use the rails in top/bottom or at side. To level it i can use epoxy. I was checking IPN and looks like IPN280 have 10mm center wall thickness. I can bolt the IPN easy to side towers

Btw UPN and IPN are bad because the welding or exist other problem?

lx (7590cm4) of IPN280 are good, but ly (394cm4) dont looks very good

btw the UPN that i use to draw the first image was just lx (925 cm4) and ly(96cm4)