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.

CService addrLocal;
            if (Lookup(strAddr.c_str(), addrLocal, GetListenPort(), fNameLookup) && addrLocal.IsValid())
                AddLocal(addrLocal, LOCAL_MANUAL);
            else
                return InitError(ResolveErrMsg("externalip", strAddr));
        }
    }
    BOOST_FOREACH(const std::string& strDest, mapMultiArgs["-seednode"])
        AddOneShot(strDest);
#if ENABLE_ZMQ
    pzmqNotificationInterface = CZMQNotificationInterface::CreateWithArguments(mapArgs);
    if (pzmqNotificationInterface) {
        RegisterValidationInterface(pzmqNotificationInterface);
    }
#endif
    if (mapArgs.count("-maxuploadtarget")) {
        CNode::SetMaxOutboundTarget(GetArg("-maxuploadtarget", DEFAULT_MAX_UPLOAD_TARGET)*1024*1024);
    }
    
    fReindex = GetBoolArg("-reindex", false);
    bool fReindexChainState = GetBoolArg("-reindex-chainstate", false);
    
    boost::filesystem::path blocksDir = GetDataDir() / "blocks";