I'll explain it for you. With your 3 wheelers, did you ever have a extended swingarm? On my atc250r, I had a stock length swingarm(85-87 length). I had to get a +1 because my new motor makes so much more power, it was un-rideable. First thing I noticed with the longer swingarm was a bigger turning radiaus and it took more effort to turn, being a by-product it was more stable in turns and I could ride it harder and longer with out the front end rising too much. Now I ride my 86 200x, it has a real short swingarm, it turns on a dime and gets awesome traction, but I have to do alot of counter-steering to keep it from going 180 when powersliding in corners, almost doing like the classic "full lock slide" that you seen 3 wheeler racers doing in corners.
Now how does this apply to quads? you ask? Same principle, a shorter swingarm gets better traction at a compromise to stability and needing for counter-steering correction. This is where the +1 forward a-arms come in, it puts more weigh on the rear, resulting in more traction, but slower turning. Due to kinda like more rake on the front end of the trike does, I noticed this when changing from a 85 250r frame to 86 250r frame(more rake). The 85 would turn sharper, faster and would require correction, where the 86 feels more planted and doesn't need as much correction. The 86 also felt far more stable.
I have a lsr framed quad with 88/89 length swingarm and +3 +1 a-arms, I also have stock framed with 89 swingarm and +3 +0 t-pin. The spindles are leaning back almost the same and camber is nearly the same. The lsr framed it turns slower and more stable, not needing much correction at all. Now comes the stock framed, it turns on a dime and tends to need correction, especially with fast turns. The difference is the +1 forward. I rode a bone stock 86 and holy cow, did it need correction in fast turns. I rode a stock 88 and it wasn't so bad, way more traction, but wasn't as stable in rough stuff.
Its a fine line between stability, traction and weight placement. Too much of any of it isn't good and could make bad results. You know how short bed and short body pickups tends to spin wheels and spin out. Then you have long bed and short front pickups that do also. My 2 tricks are great examples of this, first nission frontier, short body and 6' bed. It tends to spin out in rain and spin the tires in it also, not good stability. Other, f-350, crew cab and 9' bed. Its planted to the ground, can't get it spin out, the rear wheels only spin in mud and soft dirt(mainly due to the very street like tires and it being a dually). A truck where I used to work, it was a chevy 2500, regular cab and 8' bed. It spun out, didn't get good traction in wet stuff and for it to move in snow/mud/ice, it had to be in 4 wheel drive. It would do a mean burn-out in the dry street. It got no traction to the rear. There are other factors, if you have the ride height in the front too low and/or rear too high, it will act like it needs alot of correction and less stability. There should be 3/4"(with the rear being lower) difference between the under the frame-ground in front of the motor and frame-ground under the footpegs. For most, a 88/89 length swingarm and +1 forward a-arms is the ticket. I ride it like a trike, using the rear to turn and the front to countersteer, so its more obvious to me. I'm sure somebody else will have a different opinion.
85/86 atc 250r, very modded, lrd 310pv, +1 lsr, shortrack kit, cr250r igntion, 39 pwk, paul turner hi-rev pipe, propeg nerf bars, HREATV custom frame,
86 atc200x- 84 250r exteneded axle, supertrapp pipe, 27mm carb, works rear shock, 84 250r front end(rebuilt w/ terry kit), 350x tripples, ported head, 12:1 piston, webcam,
crf450r quad, lsr frame, swinger, antifade, hyper beadlocks and the best of everything else.
88 trx 250r pced and reinforced frame, +3+0 t-pin, 310pv, cr ignition, 39 pwk, lsr rear end, elka shocks, aftermarket radiator, lrd pipe
06 ktm450exc, full skid plate/guards, radiator fan, clarke tank, dual sport kit, reg/ins/insp, steering stabilzer
98 200exc: street plated, skid/guards, dual sport lights, stabilizer and more.
07 ktm 250xc, skids, reg/ins, dampener, good lights
2011 atc450r in the works, suspension and details need to be worked out