Quote Originally Posted by dsc View Post
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The bolt head can go from the top on both versions of the housing, it's an M4 bolt and I have 8mm clearance on top for the head. Standard head on a caphead M4 is roughly 7.2mm.

Regards,
dsc.
Standard BS EN ISO 4762 spec caphead for M4 is 6.64 - 7.00mm dia.

There's 8mm to play with... seems to me there's plenty of room...