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.

if (txinfo.tx && txinfo.nTime <= pfrom->timeLastMempoolReq) {
                        pfrom->PushMessageWithFlag(inv.type == MSG_TX ? SERIALIZE_TRANSACTION_NO_WITNESS : 0, NetMsgType::TX, *txinfo.tx);
                        push = true;
                    }
                }
                if (!push) {
                    vNotFound.push_back(inv);
                }
            }
            
            GetMainSignals().Inventory(inv.hash);
            if (inv.type == MSG_BLOCK || inv.type == MSG_FILTERED_BLOCK || inv.type == MSG_CMPCT_BLOCK || inv.type == MSG_WITNESS_BLOCK)
                break;
        }
    }
    pfrom->vRecvGetData.erase(pfrom->vRecvGetData.begin(), it);
    if (!vNotFound.empty()) {
        
        
        
        
        
        
        
        pfrom->PushMessage(NetMsgType::NOTFOUND, vNotFound);
    }
}
uint32_t GetFetchFlags(CNode* pfrom, CBlockIndex* pprev, const Consensus::Params& chainparams) {