I too had no issue at 1+ 50 mix w/ nothing added. I did lower my times a bit but eventually found that slightly longer times gave better negatives in sheet film. I never paid much attention to the 10ml per sheet of 810/roll of 35 as I had been using rodinal for a while before I knew that "rule". Once I found out I upped my amount of liquid. I did not see much if any difference but I follow that rule now.
I switched over to rollo pyro for LF negs for contact printing but the rodinal was easy, cheap with great results