If really deep pits your options are three. One have a new set of barrels made at very high cost. Two have it sleeved at moderate cost but risk major balance changes. Or three put brileys subgauge tubes put in it and shoot a heavy fence post. I guess your fourth option would be do nothing. I feel your pain.
Personally I’d send it back to GB and have the best sleeve job available done. The best get the weight close to original and are seamless. Cheap sleeve jobs are like poor circumcisions. Just hard to even look, at much less call our own. JMO.
