Drilled oversize mounting holes and countersunk 0.080" panel for bugle head mounting screws. Layout of airspeed indicator. Thought the airspeed housing would clear mounting nut-plate but too close by 1/8". Had to remove nut-plate. Used 3-1/8" flanging tool to cut mounting hole for instrument. Face of airspeed indicator was very tight against 0.080" panel, required filing with half-round to provide clearance. Squared case of AI with bottom of panel and drilled instrument mounting holes.