I was unhappy with the battery hold-down in my car and just upgraded to a more secure design normally used in performance boats:
http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?productId=442499&catalogId=10001&langId=-1&storeId=11151&storeNum=10109&subdeptNum=10548&classNum=10551
It is one helluva piece. The bottom tray and top retaining clamp are very heavy plastic. The long screws and nuts are stainless. The bottom tray attaches to the car using four, user-supplied 1/4" cap screws. I added aluminum straps between each pair of screws to provide more holding strength through the car's sheet metal than plastic alone. I'm sure this is overkill. The plastic appears stronger than my battery case. (I have no affiliation with the vendor. I just like this particular part.)
http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?productId=442499&catalogId=10001&langId=-1&storeId=11151&storeNum=10109&subdeptNum=10548&classNum=10551
It is one helluva piece. The bottom tray and top retaining clamp are very heavy plastic. The long screws and nuts are stainless. The bottom tray attaches to the car using four, user-supplied 1/4" cap screws. I added aluminum straps between each pair of screws to provide more holding strength through the car's sheet metal than plastic alone. I'm sure this is overkill. The plastic appears stronger than my battery case. (I have no affiliation with the vendor. I just like this particular part.)
Joe Piernock, Paoli, PA
1972 914-3.2, 1974 Capri, 2013 GTI
1972 914-3.2, 1974 Capri, 2013 GTI