You can make a 1.060 beer with a single draining of the mash tun after you vorlauf?
If your efficiency is 75% then you are doing that with 11 pounds of malt on a 5 gallon batch and that is certainly impressive.
You should write up your exact techniques so others can learn how you are able to achieve efficiencies on a no-sparge many don't quite get with a batch sparge or fly sparge.
I'd guess most home brewers aren't getting nearly 100% conversion efficiency. Their LHBS mill gap is set pretty wide, they don't pay attention to mash pH, etc. If you *can* get full conversion, then calculating lauter efficiency is simple and very accurate, in my experience. In the last 25-30 batches I've not missed my target efficiency by more than 3%.
On my last no-sparge, I used 8.5 lb of grain and 4.9 gal of strike liquor. The theoretical maximum efficiency would be about 72%. I ended up with 3.0 gal of 18.2°P wort, which is ~69% efficiency. So apparently that mash only reached ~96% conversion. That would be equivalent to using 14.2 lb of malt to make 5 gal of 1.075 beer.
To get 5 gal of 1.060 wort post-boil (6 gal at 1.050 pre-boil), mash 11.5 lb of grist (77% AICG) with 7.4 gal water. That's ~75% efficiency. If your conversion efficiency is only 80%, though, the overall mash efficiency will be 60%. If it reaches 90% conversion, the overall efficiency will be 68%, etc.