I often find this with pistols, the Slavia ZVP is an example.
I think with the MK2 Scorpion sight you could either file a little off the top of the rearsight or elongate the holes that the 2 screws go in if the blade is on the lowest setting
http://www.proteksupplies.co.uk/bsa-...day-parts.html --scroll down to see the blade.
Another possible solution is to get another scrap foresight base and then cut a piece of steel or plastic to the height you want and glue it into the base.