I've used pH 10. It doesn't do anything bad.
Optimal is actually 7.5- 8. Bacteria doesn't do well in alkaline conditions for the most part. But I haven't noticed anything out of the ordinary when I've added too much lime.
Three A+ jars were definitely 100% colonized. Shook up the jars and mixed each jar of mycelium with 3 jars of field capacity substrate balanced to 7.75 Ph consisting of coir and spent coffee grounds PC'd for 90 minutes last night. Paid attention to get a good mix into the corners and edges then leveled the surface as best I could. Put the three 6 qt. tubs into the IC (Incubation Closet) and will try and maintain 78-80F for the next 10 days. I will add a casing and put them into fruiting conditions on 5 May to celebrate Cinco de Mayo. This will be my only chance for shrooms in May. Starting another grow this weekend for June.