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.

/** Average delay between trickled inventory transmissions in seconds.
 *  Blocks and whitelisted receivers bypass this, outbound peers get half this delay. */
static const unsigned int INVENTORY_BROADCAST_INTERVAL = 5;
/** Maximum number of inventory items to send per transmission.
 *  Limits the impact of low-fee transaction floods. */
static const unsigned int INVENTORY_BROADCAST_MAX = 7 * INVENTORY_BROADCAST_INTERVAL;
static const unsigned int AVG_FEEFILTER_BROADCAST_INTERVAL = 10 * 60;
static const unsigned int MAX_FEEFILTER_CHANGE_DELAY = 5 * 60;
static const int64_t BLOCK_DOWNLOAD_TIMEOUT_BASE = 1000000;
static const int64_t BLOCK_DOWNLOAD_TIMEOUT_PER_PEER = 500000;
static const unsigned int DEFAULT_LIMITFREERELAY = 15;
static const bool DEFAULT_RELAYPRIORITY = true;
static const int64_t DEFAULT_MAX_TIP_AGE = 24 * 60 * 60;
static const bool DEFAULT_PERMIT_BAREMULTISIG = true;
static const unsigned int DEFAULT_BYTES_PER_SIGOP = 20;
static const bool DEFAULT_CHECKPOINTS_ENABLED = true;
static const bool DEFAULT_TXINDEX = false;
static const unsigned int DEFAULT_BANSCORE_THRESHOLD = 100;
static const bool DEFAULT_TESTSAFEMODE = false;
static const bool DEFAULT_ENABLE_REPLACEMENT = true;
static const bool DEFAULT_FEEFILTER = true;
static const unsigned int MAX_BLOCKS_TO_ANNOUNCE = 8;
static const int MAX_UNCONNECTING_HEADERS = 10;
static const bool DEFAULT_PEERBLOOMFILTERS = true;
struct BlockHasher
{
    size_t operator()(const uint256& hash) const { return hash.GetCheapHash(); }
};
extern CScript COINBASE_FLAGS;
extern CCriticalSection cs_main;