Sadly, lots of dead photos in that thread.
I've only got one Foundry renaissance commander, so strictly speaking not a knight. The figure is smaller than modern GW plastic Freeguild, and significantly smaller than the over-sized GW Empire Knights of the recent past.
I'd say the size difference doesn't matter too much. For example, you could mount the Foundry figure on a GW horse, and it would still look OK. But I'd also say that you might not want to put the Foundry figure amidst GW figures in the same unit. The size difference is precisely on that level where some say it's OK, but some others (me included) say it's too much.
Sorry, no photos.
-Z