in v0.12 https://github.com/bitcoin/bitcoin/pull/7081 (by @luke-jr) was merged adding `-bytespersigop` (with default of 20).

this is preventing simple bare multisig transactions from being accepted into mempool when the size is < 400 bytes.  
eg; https://gist.github.com/rubensayshi/ac4f617207f7a50559e85d61c05800be

from 1-of-7 and onwards they are accepted because the ratio of bytes:sigops is high enough.  
also having 2 or more inputs will work because it again tips the ratio of bytes:sigops over.

the reason mainly being that `GetLegacySigOpCount` calls `GetSigOpCount` with `fAccurate=false`.

It looks like changing `GetLegacySigOpCount` to use `fAccurate=true` would cause side effects in the few other places (`ConnectBlock`, `CheckBlock`, `CreateNewBlock`) and simply adding `fAccurate` as arg to `GetLegacySigOpCount` would affect the value stored in `CTxMemPoolEntry.sigOpCount` which in turn affects a bunch of other things.

LOCK(pfrom->cs_feeFilter);
                pfrom->minFeeFilter = newFeeFilter;
            }
            LogPrint("net", "received: feefilter of %s from peer=%d\n", CFeeRate(newFeeFilter).ToString(), pfrom->id);
        }
    }
    else {
        
        LogPrint("net", "Unknown command \"%s\" from peer=%d\n", SanitizeString(strCommand), pfrom->id);
    }
    return true;
}
bool ProcessMessages(CNode* pfrom)
{
    const CChainParams& chainparams = Params();
    
    
    
    
    
    
    
    
    
    
    bool fOk = true;
    if (!pfrom->vRecvGetData.empty())
        ProcessGetData(pfrom, chainparams.GetConsensus());
    
    if (!pfrom->vRecvGetData.empty()) return fOk;