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.

{
    assert(pindex->GetBlockHash() == view.GetBestBlock());
    if (pfClean)
        *pfClean = false;
    bool fClean = true;
    CBlockUndo blockUndo;
    CDiskBlockPos pos = pindex->GetUndoPos();
    if (pos.IsNull())
        return error("DisconnectBlock(): no undo data available");
    if (!UndoReadFromDisk(blockUndo, pos, pindex->pprev->GetBlockHash()))
        return error("DisconnectBlock(): failure reading undo data");
    if (blockUndo.vtxundo.size() + 1 != block.vtx.size())
        return error("DisconnectBlock(): block and undo data inconsistent");
    
    for (int i = block.vtx.size() - 1; i >= 0; i--) {
        const CTransaction &tx = block.vtx[i];
        uint256 hash = tx.GetHash();
        
        
        {
        CCoinsModifier outs = view.ModifyCoins(hash);
        outs->ClearUnspendable();
        CCoins outsBlock(tx, pindex->nHeight);