As long as the rocket slide easily on the launch rod, I don't think there should be any problem. If there is binding, scraping, and such, you might need a smaller diameter launch rod.
I'd check the diameter of your stainless steel rod with the calipers to make sure the rod is in fact 1/4".
If all else fails, you can buy a length of 1/4" cold rolled steel very inexpensively at Home Depot/Lowe's/Menard's.
Kit (AKA Cranky Kong)
Total Total Impulse as BAR: 7,753.69 Ns (Equivalent to a 51% M motor.)
=| Calirado, Colofornia...what's the diff anymore? |=