That would've changed the potentials a little bit. The specialty grains with less potential would've been a higher percentage of the grist in the calculations

...

Yes, you could use a "307" LDK grain. The problem is 307 is not actually a very good estimate. In The Calculator there is a fudge factor used called "efficiency"

Which compensates for this estimate being perhaps a tad high

In the CE calc there are no fudge factors to fudge a too high estimate. You would need to drop the conversion efficiency from 99% to about 95% to act as a fudge to make the numbers work. But 99% conversion is realistic and does make sense, as the Course Grind conversion should be about 1-1.5% worse than the Fine Grind which is the definition of 100% conversion

Course Grind is 0.7mm, Fine Grind is 0.2mm, at least in the UK and I would expect most BIABS to be somewhere between those two extremes. I am using 0.5mm now.

Having to fudge the numbers by decreasing the conversion efficiency to lower the potential of an artificially too high LDK value would not be ideal.

The 307 value would be a good value, if we treated it as a Dry Basis value, it's basically 80%, but in The Calculator it's used as an As Is value, which means it's circa 4% too strong. Which means all the efficiency calcs in the previous calculators are circa 4% out.

So, continuing to use this value, at least with out adding 4% moisture correction to it, will continue to propagate what I believe is actually an error.