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.

{
public:
    bool operator()(const CTxMemPool::indexed_transaction_set::const_iterator& a, const CTxMemPool::indexed_transaction_set::const_iterator& b)
    {
        uint64_t counta = a->GetCountWithAncestors();
        uint64_t countb = b->GetCountWithAncestors();
        if (counta == countb) {
            return CompareTxMemPoolEntryByScore()(*a, *b);
        }
        return counta < countb;
    }
};
}
std::vector<CTxMemPool::indexed_transaction_set::const_iterator> CTxMemPool::GetSortedDepthAndScore() const
{
    std::vector<indexed_transaction_set::const_iterator> iters;
    AssertLockHeld(cs);
    iters.reserve(mapTx.size());
    for (indexed_transaction_set::iterator mi = mapTx.begin(); mi != mapTx.end(); ++mi) {
        iters.push_back(mi);
    }
    std::sort(iters.begin(), iters.end(), DepthAndScoreComparator());
    return iters;
}
void CTxMemPool::queryHashes(vector<uint256>& vtxid)