Do you cut the tip off the inverted bolt? As they foul the gearbox under certain circumstances and have been known to crack the housing. Are you aware that it's only 3 more bolts (all accesible with an air gun) that holds the subframe in place. The front engine stabiliser, then n/s subframe bolts. There is enough give in the o/s bushes to allow the frame to be levered down to R&R the bolt.
Also, how's your liability insurance? As the bolts are not fitted correctly, should one fall out, you will be liable in the event of any costs incurred. Whether that's damage to parts or life.