I don't feel that the 5105 is heavy for limbing, just cumbersome. Fat. Centre of gravity too spread out in the crosswise direction. I think it would probably rate among the very best of all time for a 50cc blocking saw. I bought it with that in mind. Certain kinds of power are kinda addictive. Smooth, torquey power does that to me somehow. I expect the 5105 to have that in spades, if the 420 is any indication. I bought it to replace my old jonsered 590's which I want to use more sparingly. The 5105 will never handle as nice, but I am hoping it has a similar kind of power (hopefully a wee bit more). We'll see when I actually use it soon. Most of my work is clearing downed/leaning trees on fenceline, falling dying/dead trees (snags), and general clean-up/pruning.
Damn, I still need a super-nice handling 50cc saw...lol. Maybe a 550xp (with a sidestand), as it would drive me crazy to have the thing falling over all the time. And I hate the orange and grey colour scheme that looks like crap almost immediately. Eventually the autotune will be perfect. Always, every time, every saw. Then I will buy one. Although I would prefer a red version, but there is no further development coming to that line. Unfortunately, another legendary brand will be gone.