Mines for solo play

[triangular_cube]

Is there a way to have mines come up unknown to the player putting them on the board for solo play?  Right now, when I put a mine on the board, I see the value with the mask marker on it.

When I play solo on vassal, I tend to mark minefield hexes with a different counter and only drop the minefield itself down once a unit has tripped it. It retains the surprise value, but obviously results in a less thought out defense. 

You just have to make your own conversion rate for the number of randomized minefield counters to place versus the prescribed instructions in the scenario book.