Let me preface this by saying the swingarm is overbuilt...  by about 200%. Liabilities, etc... -you get the picture. Removal of some of the gusset will not weaken the part to the point of failure, and in fact, before I added material back in I test rode the bike for a week.

Most of the short work is done with an angle grinder. I used a 4" disc on mine. I had the wheel made first and mounted the tire. It was an unfinished wheel at this point but it doesn't matter if yours is or not.

I can't give you exact measurements as I no longer have the bike. But I did take a some pics.

All modifications were performed with the swingarm off the bike.

For the initial fittment you will mount the wheel with the caliper bracket, hub dampener, and the spacers square in the swingarm. The tire will make contact with the swingarm just squeeze it in for now. This will give you your reference marks for metal removal. I used a silver sharpie to highlight the areas in question. Keep in mind that when you mount the wheel normally you have to push the wheel forward in the swingarm to get the belt on. You will have to remove extra material, forward of your marks, for this.

Onto the pics:

There is some extra work done on some of the sloppy welds and casting, you don't have to do this. You see the hole created, it's part of the hollow casting. This area got a plate welded back on to cover the hole. It's not necessary, but I did to give it a factory look. (details where you don't often look make a difference to me).

I don't know if you can tell but I tried to contour the modification, again it's the finish details that shine thru. If you look at your stock swingarm you can see from these pics a lot of  the left side gusset was reshaped. Since the right side gusset was fitted and welded tight to the arm it was not necessary to re- weld that side. If your is not you may have to run a bead back onto the arm depending on how much material and welding you remove.

Here's the wheel mounted back on:

Keep in mind that tire deflection will take place at the contact patch so if the clearance looks tight in the gusset it'll probably be OK in the real world. Like I said mount it and test ride it. If you see any rubbing you'll know what to do. 

Here's some close ups: (Hope you can make sense of these):

The first pic below. You can see a sharpie mark. I ended up grinding out more material here and adding gusset to the outside of the existing material than reshaping it.

Here's some with metal welded back in:

Actually this was the second time it was welded to cover some voids I created while grinding.

Here's where the plate that got welded to cover the hole I formed early on in the process.

You can see in the above pic the finished thickness. The outside of the gusset is curved so I had to weld 3 pieces of 6061 aluminum stock to the gusset. Make sure if you do this that you maintain your belt clearances. That's why my reinforcement is not wider in this area.

BTW I never took the bearings out. Just cleaned them out so the grease wouldn't ooze all over the place while welding. I repacked them afterwards and they were fine. That's your call though...