Over-sparging with small grain bills

[LovesIPA]

I typically get between 85% and 90% mash efficiency with my setup. I have brewed Biermuncher's Centennial blonde ale a couple of times and I've always overshot the gravity by quite a few points. The beer has come out good so I haven't complained.

But if I wanted to brew the recipe to the real OG, I have to cut down on the grain bill quite a bit. Instead of using the 8.25 pounds of grain for a 5.25 gallon batch, I would need to use 6.45 pounds. This is by far the smallest grain bill I've ever brewed with and I'm worried about over-sparging. I haven't experienced it yet but I'm wondering if it's a real concern or if it's not something that I'm likely going to run into. I fly sparge and would need to run 6.25 gallons of water through the grain bed to get my target boil volume. That seems like I would be over-sparging, if there is such a thing.

I think my only other option would be to use more grain, but stop sparging at a certain point and then top off the kettle with water.

 

[Cyclman]

I have read that you don't want to sparge past when the gravity coming out of the mash is below 1010. I tend to brew bigger beers, so the few times I've checked it's always been above that.

Oversparging can cause astringency, I've tasted beers where that may have been the cause, but never had one myself.