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.

indexed_transaction_set::const_iterator it2 = mapTx.find(txin.prevout.hash);
                if (it2 != mapTx.end())
                    continue;
                const CCoins *coins = pcoins->AccessCoins(txin.prevout.hash);
		if (nCheckFrequency != 0) assert(coins);
                if (!coins || (coins->IsCoinBase() && ((signed long)nMemPoolHeight) - coins->nHeight < COINBASE_MATURITY)) {
                    transactionsToRemove.push_back(tx);
                    break;
                }
            }
        }
        if (!validLP) {
            mapTx.modify(it, update_lock_points(lp));
        }
    }
    BOOST_FOREACH(const CTransaction& tx, transactionsToRemove) {
        list<CTransaction> removed;
        removeRecursive(tx, removed);
    }
}
void CTxMemPool::removeConflicts(const CTransaction &tx, std::list<CTransaction>& removed)
{
    
    list<CTransaction> result;
    LOCK(cs);
    BOOST_FOREACH(const CTxIn &txin, tx.vin) {