Just remember to build in a lot of 'triangulation' in your high force areas. Slight triangulation is waay superior than parallel tubes. Never 't' into a tube without continuing that path of force on the other side of that tube into something solid, ie; main frame rails.
Example; forward head loop into door bar then down into main frame or lower main hoop. You stop at the door bar and a hard hit on the head loop will collapse that door bar and it all comes down around your head either trapping or crushing you.
Front to rear Triangulation also gives you a 'bridge' type effect to your chassis for more precise suspension tuning. A flexible chassis is impossible to make consistent.