At 13" vs. 12.88", the Wally/JCI 29DC is literally just 0.12" wider than the 27. You can see that the 27 allows the handle holder to jut out, while the 29 just goes straight up.
Weight is 61 and 53 respectively. So my 27 is about 87% the battery.
Rating is 125 Ah vs. 115. Because of the weight discrepancy, I suspect that testing would show the variance to be greater than that. If we believe the 125 Ah figure, then just going by weight, that puts the 27s at 109 Ah. This is more than Mex's "seven and six tenths" figure, but if those were his real test results, then that would be good enough for me.
But if the 29s have a "whopping" 15% greater capacity, then that could actually get me 8 days vs. 7 before I need to fire up the genny.
Since I never get a vacation longer than 3 days anyway... I guess I'll get over the loss. In fact... those 29s are more dough and I don't need the extra capacity. So... I actually made the prudent business decision for my family. Yeah! THAT sounds good!