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(cs);
        std::pair<double, CAmount> &deltas = mapDeltas[hash];
        deltas.first += dPriorityDelta;
        deltas.second += nFeeDelta;
        txiter it = mapTx.find(hash);
        if (it != mapTx.end()) {
            mapTx.modify(it, update_fee_delta(deltas.second));
            
            setEntries setAncestors;
            uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();
            std::string dummy;
            CalculateMemPoolAncestors(*it, setAncestors, nNoLimit, nNoLimit, nNoLimit, nNoLimit, dummy, false);
            BOOST_FOREACH(txiter ancestorIt, setAncestors) {