You are NOT a mechanical engineer or if you are well, I will stop there. I'm not and listen up, I worked building various drag cars some of which ran the 1/4 mile at over 200 mph. Motorcycles? let's just say I pretty much know what I'm talking about there too. Mostly anyway.
Your lack of connection between safety and wobble could get you killed. Why? For one a massive failure to realize how quick a wobble can turn into accident.
(1) You CANNOT weld on spring steel used in a leaf spring, the heat treat is what gives the springiness to the part, welding kills that since the heat induction and cooling process overthrow the original which is what made the steel part springy. NOBODY welds on spring steel unless they have not a clue. You will lose either the spring tension or worse leaf will break close to a weld point. I've seen it before. NO mechanical engineer on the planet would approve that!
(2) You have cut the leaf it appears, that GREATLY increases the spring rate just like cutting a coil spring. It will be much stiffer than the entire spring was because it is shorter, the same forces going into it have less leverage because the working arm there is shorter. Witness your one inch total of up and down travel, not enough, too stiff. Normal rear on one of these bikes uses around three inches normally. The one inch makes it much easier for spring to break since it cannot work as a spring nearly so easy. Shortening it made it much closer to a solid arm or bar.
(3) The puny bolts you have at the back end of the leaves are extended as compared to the OEM ones and they are also not centered and pinched over the arm both of which made them much much stronger. Your bolt is long enough that with no suspension because of (3) the stress will be heavily on that bolt and break it or swing arm boss in a matter of minutes. Worse because bolt not supported on both ends, it is now a lever worked up and down in the hole by the leaf. Weakest part of the whole thing, take a look at how leafsprings are mounted on the ends, ALWAYS from BOTH SIDES of the eyelet NOT ONE. One side mounting is guaranteed twist to wobble.
(4) You don't have enough leaves there at all, too thin. Too much force has to be absorbed by the two there, they will break. The loss of heat treat from the weld will add to that. So will essentially being a hardtail.
(5) The difference in lengths producing interference arcs in suspension travel. Already called out. Spring and arm are fighting each other, another reason why you only have one inch in travel, go further and parts will likely break.
(6) With assumed rubber bushings in the leaf eyelets, since eyelets are outside of the swingarm instead of centered over it and pinched on both sides the swingarm will wobble in its' play at frame since what is supposed to damp that out is missing, your leaves not only flex up and down but can flex twist as well, the rubber does nothing to damp that out, rather giving space to twist. Think about why the OEM swingarm is not rubber mounted to frame, it has bearings to help positively stop that twist. You with the leaves though have added forces to let more twist in the 'suspension' if you could call it that, I certainly don't. More like mounted solid as a rock with all forces going into those puny little rear bolts. BIG mistake my friend.............................
Leaf springs are NEVER considered suspension only, they cross the line to be part of the structure (frame) guaranteeing driving wheel(s) stay straight, look how they are used in cars and trailers. They ceased being 'suspension only' parts when you began to ask them to stop wobble which is what this thread seems to be about! Suspension alone does NOT stop directional integrity yet clearly you have asked the leaves to hold that integrity.
Again, no insult intended, if you were my best friend I would be telling you even more.
DON'T, your basic idea is dangerously flawed. I just got a free Nighthawk 750 because someone simply extended swingarm and the frame runners at top to mount standard OEM shocks further back by 5 inches. The frame extensions were 3/8" steel plate but extended like that they flexed and then tops of shocks moved side to side to make for an uncontrollable wobble over 30 mph.