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.

pindexNewTip = chainActive.Tip();
            pindexFork = chainActive.FindFork(pindexOldTip);
            fInitialDownload = IsInitialBlockDownload();
            nNewHeight = chainActive.Height();
        }
        
        
        
        if (pindexFork != pindexNewTip) {
            uiInterface.NotifyBlockTip(fInitialDownload, pindexNewTip);
            if (!fInitialDownload) {
                
                std::vector<uint256> vHashes;
                CBlockIndex *pindexToAnnounce = pindexNewTip;
                while (pindexToAnnounce != pindexFork) {
                    vHashes.push_back(pindexToAnnounce->GetBlockHash());
                    pindexToAnnounce = pindexToAnnounce->pprev;
                    if (vHashes.size() == MAX_BLOCKS_TO_ANNOUNCE) {
                        
                        
                        break;
                    }
                }
                
                int nBlockEstimate = 0;
                if (fCheckpointsEnabled)
                    nBlockEstimate = Checkpoints::GetTotalBlocksEstimate(chainparams.Checkpoints());
                {
                    LOCK(cs_vNodes);
                    BOOST_FOREACH(CNode* pnode, vNodes) {