Its really irritating how a simple head cold completely removes my ability to do anything.....hopefully, I'm back now.
Stirling work, N.A....I have checked all your numbers, the only error I found was 156mm for the head tube instead of 196 on the 58cm....the programme appears to compensate by elongating the forks to keep the "stack" correct.
It looks to me like they are using 2 different fork offsets, an "industry standard" 45mm offset for most of the sizes, and a slightly shorter (41mm) for the 2 biggest sizes. They don't seem at all concerned to have the handling the same across all the sizes, they are happy to use head angles from 70.5 deg to 73 deg. with a 45mm offset (and fairly different trail values on N.A's diagrams) so I imagine the reduced offset is designed to keep the wheelbase down as the reach increases on the big sizes, but on the plus side it might make the big bikes less likely to shake their head.
So I think the 52 has an offset of 45mm and approximate ETT and stack of 538 and 387 respectively, not 530 and 379 with 53 offset.
To finally get back to the question of a choice between the 49 and 52 frame sizes......
As you might expect from a 2 deg change in head angle, there is a fair difference in reach with the 2 bikes, in the region of 11mm. Once you add the extra headset spacers to make up for 26mm difference in stack, the small bike will be another few mm shorter reach.
But there are other imponderables.....
If this is the OP's actual bike, is it sensible or even possible to get another 26mm bar height? (on the smaller frame to make up the "stack" difference))
If the OP's saddle is now considerably too high, he may not need the full 26mm.
2 deg. difference in head angle will make a big difference in the handling.
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