According to this search, four current NL grounds have the capacity to beat it:
1. Meadow Lane home to Notts County 19,588
2. The Racecourse Ground home to Wrexham 15,500
3. The Shay home to FC Halifax Town 14,081
4. Roots Hall home to Southend United 12,392
ps I hope we break the record, then lose it to Forest!