i am building a tube chassis gremlin. 2x3 frame rails. my question is under the seat they say to put bars under it. i put in the middle of the door jam 2x3 out rigger and was going to run bars under the seat. but can not find out what size of bar goes there. i dont see why i can't run 1 1/2 in a X under the seat. can i get some help?