I think the tenellus looks absolutely charming :!: It's got a lovely light and airy feel to it, looks really natural too.
Trouble is it won't stay like that for long - it is a complete brute.
I thought I'd found a genuinely dwarf variety in a dealers tank once (2-3 cms tall, and about 2mm thick leaves) - it was planted in the gravel in the tank (plain gravel and no fertilisers, probably an undergravel filter as well) and spreading nicely through runners. I was so chuffed, it was just what I wanted for a tiny 22" tank. 4 weeks later with a bit of light, food and CO2 it was looking like yours - although as the tank was only 10" high, you can imagine it didn't turn out to be a great foreground plant!
I wonder if it might stay a bit smaller if you did a trendy 'sand beach' at the front and planted it it in that? You could try reducing the lights and fertilisers a bit too, but you've got your stems to consider.
Or just dig the whole lawn up and replant every month ! (Not an attractive proposition!)
Can't wait to see how it comes, and what you decide to do - the tank really is looking spectacular already, congratulations.
Mark