Wow Ray--From "I'm in a mess" (your first post) to this!--Now I think that's quite a contrast, because this is sounding good and your confidence is sounding like it's up there also.
You've gotten a great sound out of GPO, so that's a big plus right there.
This arrangement could use more harmonization, I feel. There's quite a bit of unison playing which makes it lack the power and grandeur you otherwise went for in the playing style. In a few places there is a bit of harmony, but it soon reverts to the melody. I think it'd be well worth it to keep expanding on those harmonies, and have more all the way through.
The percussion isn't bad, the snare drums seem to be doing appropriate patterns--They can just be LOuder! For that "marchy" result you said you want, you can afford to bring their levels up in the mix.
Something effective I've done before is have multiple instances of just the rolling snare, panned across the stereo field, slightly detuned from each other, and with their MIDI data slightly shifted in time--you can get a nice big marching band wall of snares that way.
How's that for a start on a critique? Others will offer feedback too I hope.
I have to admit that it is lots of copy and paste work from different versions of this song I was working with for a long time in other programmes, but I also had to create some parts from the scratch for this to make it fit together. I will remix the whole stuff and try to focus a little bit more on the percussion section.
Concerning the harmonies I struggle a lot with the counter-melodies. Is there any way to get a basic layout you can start to work with? In these kind of things I am quite increative, I suppose ;-)
I agree with Randy. I'd like the drum rolls to be more prominent. But I like the percussion! If you wanted to make it even more percussive, you could add orchestral cymbal crashes on the first beat of the bar ... maybe a triangle here and there ... the odd cannon ... okay, I'm joking about the cannon!