By, Doug Carruthers 
By popular request from our users, we reduced the minimum center to center bore spacing (SB) for vertically bored ghex down to 10ft from 15ft.
We originally set the minimum at 15ft because when bores get much closer than that, they can begin fighting each other and degrade the long term performance of the loopfield. This is especially true in areas with wide temperature swings and greatly unbalanced heating/cooling loads. However, as our users keenly pointed out, in mild climates, 10ft on center is not an uncommon configuration for a loopfield.
We maintained a default value of 15ft because, for the majority of designs, we don't recommend bores spaced any tighter but, for those that need the flexibility, you may now adjust down to 10ft centers.
As always, let us know if there is anything else you would like us to address.