G16 low speed - limit secondary opening idea?

[Canuck12345]

I am once again about to modify another G16 that will only ever be used at the lowest possible speed.

With appreciation I have received some great ideas in the past from the more knowledgeable cart guys here on the forum, such as cut secondaries, heavier springs etc. They have all done a good job at giving more low end torque and at reducing the cart speed, but I am still searching for more ideas that would completely stop the cart from accelerating to higher speeds.

To be clear, the cart will only ever be used to climb/descend steep (ish) hills with a 300-400lb load on board. From experience the value of having the clutch engaged going downhill (thus providing engine breaking), is equally as important.
Going downhill we ride the brake at the same time as the throttle to engage the clutches, this helps with run away coasting. It is going downhill that the cart wants to shift up and goes too fast for the terrain.

My latest idea (which might be crazy??), is to modify the secondary clutch so that it cannot open at all.

If the idea isn't going to cause major clutch/belt problems, I was hoping to get suggestions on how to best go about preventing the secondary from opening.

Thought about welding a ring around the inside of the sheaves low enough in the sheaves such that the belt will not contact it, but not sure that the heat from welding might make the sheaves brittle???

Also thought about simply bolting through both sheaves, but was worried they won't hold given the rotational forces.

Thought about a combo of stitch welds and bolts??

Lastly, could the spring be removed and the shaft filled with spacers?

Would anyone know why this wouldn't work and have any suggestions on how to lock the sheaves from opening?

Thanks