HC is slower than other stem plants, but once it gets established you should be able to see the new growth. I do think that trimming/topping the HC will help it to send out side shoots and spread quicker. Adding excel also really gives the HC a boost. I have pressurised co2, but definately see a growth spurt when I add excel to the tank as well.
One thing to remember, when you do get your HC growing, dont let it get too thick. Mow it down occasionally. I just learned this the hard way. My foreground was about 1.5" thick and the bottom of the mat of HC started to die and melt away. Part of it started to rise off of the substrate. I had little strands of HC breaking off and floating on top of the water. By the time this started happening, it was too late to just trim it down. I had to pull up the entire lawn of HC, in one big mat, and replant the entire foreground, strand by strand. I hated to do it, because it looked so good and took so long to get that full and thick, but it was just going to get worse if I didn't do something about it. So... just keep an eye on it further down the road.
Good luck!
-Mike B-