You seem to think your conditions are the same as mine. My mower worked just fine for my conditions at the speed I wanted to mow it. You also seem to be confused about how much a L2501 weighs with FEL and bucket, and loaded R4 with QH or maybe you just aren’t good at math.In no way will the L2501 be able to run a 6' mower. Your dealer is an idiot if he told you that. A 6' mower is almost as long and 1/3 the weight of a 2501.
I hate to break it to you, but not all grass is heavy and doesn’t grow to 6’. My land is not irrigated. It’s dryland with only about 12-14 inches of precipitation for the entire year. My land is also between 4000-5000 although the area I mowed with it is closer to 4400.
In my case, you are wrong, and my dealer was right. It’s the danger of thinking all conditions are the same and believing some specs that are cleariy wrong. I’ll leave the name calling to you though.