Okay, I have an off-the-wall suggestion for handling a low-alcohol beer. According to George Fix, a 158F mash produces the following wort composition:
Disaccharide - 41%
Trisaccharide - 16%
Monosaccharide - 8%
Dextrins - 35%
A yeast species known as Saccharomycodes ludwigii (S. ludwigii) is used in the production of low-alcohol beer. From what I understand, S. ludwigii only ferments monosaccharides, the disaccharide sucrose, and the trisaccheride raffinose. It will not ferment maltose or maltotriose. Wort contains only a small amounts of sucrose and raffinose. The primary disaccharide in wort is maltose; hence, real attenuation of wort produced from a 158F saccharification rest is going to be around 8% of the original extract.
If you think about it, most normal gravity craft beers have an apparent extract (AE) of around 2.5 to 3 degrees Plato (an F.G. of 1.010 to 1.012) and an original extract (OE) of around 12 to 13 degrees Plato (an O.G. of around 1.048 to 1.053). I know that alcohol is a flavor carrier; therefore, its effect on beer taste cannot be overlooked. However, what we perceive as body is the real extract remaining after fermentation is complete. Real extract is the percentage of sugar that is left in solution weight by volume (w/v).
Degrees Plato is a great scale to use when brewing because it can be used to tell us how much sugar is in solution w/v. For example, a 1.040 wort contains 10% sugar w/v.
real extract (RE) = (0.8114 * AE) + (0.1886 * OE)
RE = 0.1808 x OE + 0.8192 x AE
Plugging 12 into OE and 3 into RE yields:
RE = 0.1808 x 12 + 0.8192 x 3 = 4.6272 degrees plato
We need to determine what OE we need to start with to obtain an RE of 4.6272 degrees.
As S. ludwigii is going to attenuate a 158F wort by approximately 8%, we need an OE of
4.6272 / 0.92 = 5.03 degrees Plato, which equals an O.G. of approximately 1.020
Hence, a 1.020 gravity wort fermented with a S. ludwigii should have the same RE after fermentation is complete as a 1.048 fermented with a normal brewing strain.
alcohol by weight (ABW) = (OE - RE) / (2.0665 - 0.010665 x OE)
ABW = (5.03 - 4.6272) / (2.0665 - 0.010665 x 5.03) = 0.2%
alcohol by volume (ABV) = ABW x 1.25
ABV = 0.2 x 1.25 = 0.25%
Now, the final gravity of the beer is not going to be the same as if we had started with a 1.048 wort. That's because there is less alcohol in solution.
Working backwards from OE and RE yields the equation:
AE = (RE - 0.1808 x OE) / 0.8192
Plugging 4.6272 into RE and 5.03 into OE yields:
AE = (4.6272 - 0.1808 x 5.03) / 0.8192 = 4.54 Plato or an F.G. of 1.018