I am taking over the management of a backyard vineyard with 26 vines located in Almaden Valley of San Jose CA. The owners do not know which vines are cab and merlot. I will need to identify that. the trellis style was hard to identify but I think it is called a wye or double cross arm. The vines are planted 6’ spacing and are divided into 4 cordons. So I assume this will by managed like a TWC with a divided canopy. My question is why are there four wires on the top cross arm and what is the use of the inside two wires? since this is a 4 cordon system this will of course double the number of buds. The cordons are spur pruned and typically 3’ long. So I calculate 9 spurs each of 4 cordons and 2 buds per spur is 72 buds which may be overcropping the vines. Would it be advisable to put vines at 3’ spacing and shorten the cordons? Also 8 vines are dead. I looked at a cross section of a cordon and did not see streaking of the wood to indicate infection. The cordons are wrapped around the trellis wires and may be girdling but I do not know. Would it be worthwhile to attempt grafting replacements or simply buy new vines? I have no experience selecting grape rootstock. I have not grafted grapes, I have attempted citrus with limited success.