10mm... and not to open a can of worms that rarely shuts, but how many pounds do ya plan on torquing the slider bolts to? Mine are at 29#, about average for what the last discussion covered.
If I'm not mistaken the debate continues... but seems someone had to order a custom seat that had a 30 degree bend in it to counteract the twisting of the frame after torquing to 194 pounds (um, too much), and someone else claimed they lost the engine due to the 4.5 pounds of torque they applied (not enough)...
Let's hear what you do it at...
C