Do i really need sub frame connectors???

I saw somewhere on line,some connecters made of 2 pieces of smaller size pipe welded side by side,with a plate on the front end,and a box type end welded on the rear.They were for sale,new, on some web site.Maybe Ebay{I can not find them anywhere}
I have access to pipe at work,for free! I have single wall [schedule 40],also Double wall [schedule 80].Should I use 1 piece of Double wall with ends welded on, or use 2 pieces of single wall welded together with ends welded on?
The Double wall is 1.25 inch pipe,the single wall is 1 inch pipe.I am leaning toward the double wall.I just dont know! The 1.25 is about 3/16 thick.The 1 inch is about 1/8.
What do yall think?