From the BGA:

5. Non-Lifting Parts. For sailplanes where the Leading Particulars specify a maximum weight
of non-lifting parts, it will additionally be necessary to weigh the wings to enable the weight of the
fuselage and tailplane to be calculated; this is the empty weight of non-lifting parts.


I can't say what the significance of exceeding the max would be, but from general life experience exceeding the max of anything is usually a bad idea.

RC