SPC UCA with stock washers

I'm installing the SCP adjustable UCA kit. The washers with the SPC kit seem weak by comparison with the stock washers. The stock washers are asymmetric compared to the flat washers of the SPC kit but much beefier.
Wondering if you guys are using the stock washers with the concave side of the washer facing the poly busing of the SPC UCA, or opposite?

Thanks in advance
Bob

 

I used the washers that came with the SPCs without any issues but I would think either one of them would be fine.

 

They are concave because the rubber doesn't have the density to hold the shape when torqueing down . Use the ones that came in the SPC kit.
Just did this, they are fine

 

I spoke with SPC about this last week. They said do NOT use the factory concave washers, only the ones supplied by SPC. One against the nut and one against the bolt head.

 

Thank you for the info. I got them installed with the SPC washers.
Are the SPC UCA arm bushings vulnerable to wind up?
Can the long bolt be torqued with the suspension hanging or does it need to be sitting on the wheels?
The instructions don't mention anything, and it would be real tough to torque that nut with the wheel on.
I'm asking because my 2.5-3" toytec Aluma lift is resting at 5" with the wheels on - nothing else is torqued.
LCA bolts are barely snug, lower shock bolt is barely snug.
half shafts seem happy- spinning no issues, etc.
I have not driven it yet.

 

It doesn't matter & it is a PITA to do it w/the tires on.