I've contemplated eschewing the swivel 2-bolt mount in favor of a 4-bolt mount directly to the cross-slide. The video shows the 4-bolt direct mount is at the edges of the cross-slide, and into the dovetails. In may case, drilling and tapping the dovetail areas would constrain bolt diameter, probably to M4, while doing the same outside the dovetails constrains bolt length to 5mm or so, and would probably require custom facing/parting the bolts so they don't protrude past the bottom of the cross-slide.
My instinct tells me bolting through the dovetail area is the better choice, I can always add another bolt making it a 6-bolt mount if needed.
View attachment 488593