The 4.5 line is more than heavy enough for the Yamame. Without watching your cast, I would bet that you are extending the forward cast too far (trying for every inch of distance) which prevents you from ending with an abrupt stop. The casting stroke with a Yamame is fairly quick, with abrupt stops on both the back cast and forward cast. Try to stop your back cast at 12 or 12:30 and your forward cast at 10:00 (then raise your rod tip to 10:30 as your line turns over). Practice with just the soft hackle, no weight and no strike indicator. With a short, quick forward cast and a hard stop, you can cast a size 3 line with a Yamame. Not sure about the Hera rod - I've never used one, but the principle will be the same, quicker casting stroke with hard stops and the 4.5 line might be sufficient. I have a taper for a twisted fluorocarbon line that I thought was too heavy for a tenkara rod - send me PM. I'm curious to see if it would work on a Hera rod.