I've heard of people doing that- letting the soil cycle from 6.5 to 6.8. The other thing you could do is go down to 6.6 and split the difference. 6.3 isn't that great and I would not purposely try to bring my nute solution down that low.
The other thing you can do is get in a habit of doing a regular but quite weak foliar feed with a micronutrient.