I have been operating N131JF frequently over gross on takeoff in recent years. With an empty weight of 960 pounds and a placarded gross weight of 1420 pounds, operating the plane with pilot and passenger and more than minimal fuel puts me above gross weight on takeoff.
There is no structural or performance issue with increasing the gross weight by 200 pounds. Many Long-EZs are placarded in that weight range, and there are numerous instances of Long-EZs operating at close to 2000 pounds takeoff weight, for long-distance flights.
The main limitation is the landing gear and brakes, which were originally designed for the Vari-EZE, a plane whose prototype weighed only around 700 pounds empty. The increase in empty weight equates to double the kinetic energy on landing for a well-equipped O-320 Long-EZ operating with pilot and passenger.
My Long-EZ was fitted with Cleveland heavy-duty brakes rescued from a Piper Tomahawk. The brakes were fitted over 15 years ago, and if one adds the age of the Tomahawk, these brakes were close to (or past) 30 years of operation. I have been replacing the o-rings once a year at the last 2 annuals because of leakage. The brakes were worn out, they still worked, but at the least they needed an overhaul. The high-spec Grove brakes offer 2.5 times the kinetic energy dissipation, and are better made. So...I bought a set of Grove wheels and brakes, and decided to fit them before the Bahamas trip.
The most important take-away from reading about fitting Groves on the Canard Aviators board is that the caliper float brackets are slightly different to the Clevelands. While you can theoretically fit the Groves to the existing Cleveland float brackets, the slight dimensional mismatch leads to brake binding.
The process of fitting the Groves is therefore a three-step one:

1. Remove old wheels and break down, fit tires and new inner tubes to new wheels
2. Remove axles from gear legs, remove Cleveland float brackets, replace with Grove float brackets, re-fit axles
3. Remove old Cleveland calipers, fit new Grove calipers, bleed brakes

Everything went OK except for the following issues:

- I positioned the float bracket on the left-hand wheel in the hardware sequence attached to the axle. As a result, when I fitted the wheel and trial-fitted the caliper it became clear that the caliper would not be in the correct position with respect to the brake rotor, the caliper was sitting too far inboard for the outer part of the caliper and brake pad to fit around the rotor. This was visually obvious. I had to remove the axle hardware and correct this. No big deal, it was good that the issue was visually obvious.
- When bleeding the right brake circuit, I ended up with a bubble in the line somewhere and a very spongy brake pedal. We tried to bleed the brakes from the top and the bottom, but the sponginess remained. We let the plane sit overnight, came back the next day and re-bled the circuit from the bottom and then the top, then the bottom again. This seemed to cure the problem.

After completing all of the installation and ground checking, I went out and bedded in the brakes on a low-speed taxi run, by dragging the pads to heat them, and performing several hard stops. Then I did a high-speed run down the runway to complete the bedding-in. After that, I safety wired the caliper bolts, and we were ready for action.

Impressions?
1. The pedal is slightly spongy with the Groves relative to the Clevelands. This is probably due to the greater fluid volume in the caliper, since the Groves are twin-piston calipers.
2. When you press the pedal, the plane steers and brakes immediately. With the Clevelands, there was always a perceptible delay before the plane responded
3. The braking capability is far superior. Relative to the Clevelands, the Long-EZ with Groves feels more like a road car. The nose dive is also far greater under heavier braking.

The increased heat dissipation of better brakes is a concern when you have a glass gear strut. There have been instances in the past of pilots overheating gear struts by heavy braking, which resulted in gear strut deformation. There are aluminum heat shields between the brakes and the gear strut on the plane. I beefed up the heat deflection capacity of those shields by gluing a sheet of FiberFrax to the inside of the shield (between the shield and the gear strut) with high-temperature RTV.
I do not intend to engage in heavy braking with the Groves. The purpose of the upgrade was to give me more braking power if I needed it in an emergency. On numerous occasions recently I was using the Clevelands to their limits - there was no additional braking power available. With the Groves, I can use them normally to the same extent as the Clevelands, and have ample emergency braking power if I need it.