Yeah, I've got a couple of cuttings from various species (including the Limno) currently being smushed under piles of aquarium literature, which I'll be sending to Cavan as a holiday present :P
As for your questions, the pedicels are short. Like, practically nonexistent. The biggest one I've seen thus far is maybe 2mm. The span of the leaves at the whorls tops out at about an inch. It's a tiny plant.
As for the petals... I'd have to go find a ruler to be sure, and they're a bit difficult to measure what with the corolla's shape and such, but they're at a guess maybe 7mm...
Though the plant does look similar to L. repens, especially in terms of size, the Flora of China key seems to indicate that the emersed form of L. repens has strictly opposite leaves - 'Vietnam' as you can see in the photos, is whorled with typically 3 leaves to a whorl (I do occasionally see nodes with 4 leaves, and a few with 2, but the majority are 3-leaved).
In other news, my Staurogyne repens bloomed today. I'll have to take some pictures to share... also, my Lindernia sp. 'India' has produced seeds. Very, very tiny and very, very numerous seeds. Don't think I'll be getting pictures of those, but I'll send some to Cavan so he can stick them under a microscope.