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.

return true;
        }
        LOCK(pfrom->cs_inventory);
        pfrom->fSendMempool = true;
    }
    else if (strCommand == NetMsgType::PING)
    {
        if (pfrom->nVersion > BIP0031_VERSION)
        {
            uint64_t nonce = 0;
            vRecv >> nonce;
            
            
            
            
            
            
            
            
            
            
            
            pfrom->PushMessage(NetMsgType::PONG, nonce);
        }
    }
    else if (strCommand == NetMsgType::PONG)
    {
        int64_t pingUsecEnd = nTimeReceived;
        uint64_t nonce = 0;
        size_t nAvail = vRecv.in_avail();