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.

SetMockTime(GetArg("-mocktime", 0)); 
    if (GetBoolArg("-peerbloomfilters", DEFAULT_PEERBLOOMFILTERS))
        nLocalServices = ServiceFlags(nLocalServices | NODE_BLOOM);
    nMaxTipAge = GetArg("-maxtipage", DEFAULT_MAX_TIP_AGE);
    fEnableReplacement = GetBoolArg("-mempoolreplacement", DEFAULT_ENABLE_REPLACEMENT);
    if ((!fEnableReplacement) && mapArgs.count("-mempoolreplacement")) {
        
        std::string strReplacementModeList = GetArg("-mempoolreplacement", "");  
        std::vector<std::string> vstrReplacementModes;
        boost::split(vstrReplacementModes, strReplacementModeList, boost::is_any_of(","));
        fEnableReplacement = (std::find(vstrReplacementModes.begin(), vstrReplacementModes.end(), "fee") != vstrReplacementModes.end());
    }
    
    
    ECC_Start();
    globalVerifyHandle.reset(new ECCVerifyHandle());
    
    if (!InitSanityCheck())
        return InitError(strprintf(_("Initialization sanity check failed. %s is shutting down."), _(PACKAGE_NAME)));
    std::string strDataDir = GetDataDir().string();
    
    boost::filesystem::path pathLockFile = GetDataDir() / ".lock";
    FILE* file = fopen(pathLockFile.string().c_str(), "a"); 
    if (file) fclose(file);
    try {
        static boost::interprocess::file_lock lock(pathLockFile.string().c_str());
        if (!lock.try_lock())
            return InitError(strprintf(_("Cannot obtain a lock on data directory %s. %s is probably already running."), strDataDir, _(PACKAGE_NAME)));
    } catch(const boost::interprocess::interprocess_exception& e) {