The pipe I got with my 7 1/2' dish is 4 1/2",except at the top where it's 3 1/2".If I get it welded to the other 4 1/2" piece from my 10' dish,then I will have one piece about 15- 20' which would be lots for the 10' dish.If I buy a 3 1/2" pipe for the 7 1/2'er,where could I buy such a pipe...