Different way to have battery backup on gridtie

This idea came directly from my previous post on a practical PV backup system. I have some grid tied modules nearby my battery backup shed and wanted to employ the grid tied modules to help out when the power was down. I decided to switch 6 modules into a 2 x 3 panel series string to feed the charge controller. The above diagram represents one string. It will deliver >100 VDC @ ~8A. My charge controller, an Outback FM80, can take in up to 150 VDC.
By using 120 VAC for the relay coils, it will automatically switch to DC mode if the grid goes down or you turn off the supply switch. Care should be taken switching in full sun/load conditions. It could shorten the life of the contacts in the relays. Disconnect the AC and DC sides of the system when practical.  You could install 4 RC snubbers on each relay or buy solid state relays. Either is kinda expensive. There may be no problem at all.
I'll be installing this over the next few days and I'll let you know how it works, or not...