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.

{
private:
    int bit;
public:
    WarningBitsConditionChecker(int bitIn) : bit(bitIn) {}
    int64_t BeginTime(const Consensus::Params& params) const { return 0; }
    int64_t EndTime(const Consensus::Params& params) const { return std::numeric_limits<int64_t>::max(); }
    int Period(const Consensus::Params& params) const { return params.nMinerConfirmationWindow; }
    int Threshold(const Consensus::Params& params) const { return params.nRuleChangeActivationThreshold; }
    bool Condition(const CBlockIndex* pindex, const Consensus::Params& params) const
    {
        return ((pindex->nVersion & VERSIONBITS_TOP_MASK) == VERSIONBITS_TOP_BITS) &&
               ((pindex->nVersion >> bit) & 1) != 0 &&
               ((ComputeBlockVersion(pindex->pprev, params) >> bit) & 1) == 0;
    }
};
static ThresholdConditionCache warningcache[VERSIONBITS_NUM_BITS];
static int64_t nTimeCheck = 0;
static int64_t nTimeForks = 0;
static int64_t nTimeVerify = 0;
static int64_t nTimeConnect = 0;
static int64_t nTimeIndex = 0;
static int64_t nTimeCallbacks = 0;
static int64_t nTimeTotal = 0;
bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pindex,