adding cherries to Flanders Bruin

I have a Bruin that has been souring for 4 months total now, 2 of those months at 65-70F, 2 at 80F. I tasted it the other day and it tastes very much like Rodenbach Foerbier, the unblended, unfiltered aged version of their beer only found in Belgium. It has a fairly harsh acidity to it, but in a pleasant way. The pH meter read 4.3, though I don't fully trust the device.

Question 1: When should I add cherries to it? My Wild Brews book recommends adding it at 6 months, but it also says that you want to mix it with a 'soft' beer, which makes me afraid that it becomes too acidic.

Question 2: What is a good fermentation container? Is a regular glass carboy not a good choice? They say plastic buckets would be convenient due to open mouth, but allow too much oxygen permeability.

1. I would add it around 6 months, give or take a month or so.
2. I would use a glass carboy, for just the reason you mention. I had a batch go bad when in plastic too long.

For an aging vessel I'd go with a better bottle. Check out the Mad Fermentationist blog. He uses better bottles all the time. I have a 6 year old Flanders red aging in some better bottles. I'm getting no acetic character at this point.