I could give you advice but the result might be someone's leg shot off.
Poor aim with our QHI course cannon (in 1984, by a certain George McC, God rest his soul) resulted in a pelmet, curtain rails, a pair of curtains and plaster getting shot down in the newly decorated ladies' room in the OM at Shawbury, oops..
He was supposed to be going for a stack of pint pots on an armchair - the elevation was about 45 degrees too high.