1) We agree on this. I pointed it out as some folks who have not used a grapple worry that narrow grapples cannot pick up trees which is obviously not the case. Technically they can pick up even bigger trees as they have more net lift capacity than a tractor with a larger heavier grapple.
2) Breakout force on a root that you have a tine under is affected by having extra tines. That is why rippers, which aim to maximize force on roots, have only one tine. True that if you are digging in fine sand and have extra tines they will not diminish the breakout force on the root in any meaningful way, but if there is sod or rocks or other roots in the area then the breakout force on the target root is diluted. If extra tines were of no consequence, there would be no reason for backhoes to use rippers instead of buckets.
4) I am well aware that lift at pivot point is not the important number. However, a heavier grapple (say 85lbs heavier) is actually cutting lifting capacity more than 85lbs because the grapple weight is forward of the PP. So your grapple has basically about 100-150lbs less net lift capacity than the identically constructed 48" grapple. Not such a big amount but probably 5-8% of your total lift capacity. If you had one of the typically 600lb heavy duty 72" grapples that many people advocate, you'd pay a much bigger penalty and lose perhaps a quarter of your lift capacity compared to a 48" grapple. Perhaps you have never tried to lift something you didn't have the capacity to lift. I have. Every little bit of capacity counts. As for
ballast, the same principle applies. If you have an extra 200lbs hanging off the front of your tractor, you have about 200lbs less down force on your rear tires. I have lifted boulders with my grapple that left me with barely the traction and control I needed to move despite having a backhoe mounted. Unless you want to carry around excessive ballast all the time, it does matter how heavy your FEL implements are, especially when lifting extreme loads.
5) Basically yes but the same concern about bulldozing and hitting an object off center (especially hitting a stump or big rock with the edge) is the same for buckets and grapples. Usually you don't plow into unexplored brush with a bucket but that is a typical task for a grapple. That grapple edge is a potential vulnerability. A 48" grapple has it's edge right about in line with the FEL arm so there is essentially no twisting force when you hit a stump etc. (still not great to ram a stump with skimpy CUT FEL arms!!) Note that bulldozers, which are designed obviously to bulldoze, have their "FEL" arms as close to the blade edge as possible and that those arms are fat and short. FEL arms are not designed for bulldozing and anything that increases twisting forces on them is bad.
6) In the case of grapples on CUTs, a reasonable argument can be made that cheaper is better if the cheapness is achieved through narrower grapple with only one upper arm/jaw. Cheapness can go too far however and there have been a few threads here on manufacturers who use 1/8" thin wall square tube for frames on their economy grapples. That is to be avoided. 1/4" has been shown to be perfectly adequate but it is possible to crush 1/8". I don't know exactly which manufacturers were using 1/8" in the past nor do I know if any still do. Anyone buying a grapple should ask specifically what wall thickness is used though. NEVER buy a 1/8" square tube wall thickness grapple unless the ONLY thing you intend to do is pick up loose brush.
