Good seeing this tread before my ELCAN 1x4 gets here tomorrow or the next day, I also took advantage of the ELCAN sale....
In my experience with slotted caps, it is very important that the fit of the tool or coin you use it tight. Any looseness in the fit of the tool will result in damaging the slot. So I usually make a tool out of a metal washer, that is a tight fit to the slot .....My Trijicon MRO has the same slotted cap on the top, same deal with that one and a few other devices I have with slotted caps
Flat blade screw driver is not idea because most slots are cut into the cap concave, so a flat blade does not sit deep enough into the concave slot and slips out and causes damage, That is why a coin or washer can fit better as the outer roundness can allow it to fit the concave better for maxim contact
Just a quick look and its exactly as I suspected. slot is concave into the cap, a flat bottomed tool is not going to get enough purchase on the cap, the edges will slip out and mangle that slot
My Aimpoint came with a tool specific to removing those caps, it has convex shaped sides that fit those slots concave
here you can see it beside a metal tool, also with the correct convex shape to fit those slotted caps properly