so after watching episode 7, was thinking that the star destroyer looked much smaller then an ISD, and I hope that's right. making that a medium sized ship for armada would be great, what do you guys think?

3000 meters long, so nearly double an ISD's 1600m. Epic size, maybe?

so after watching episode 7, was thinking that the star destroyer looked much smaller then an ISD, and I hope that's right. making that a medium sized ship for armada would be great, what do you guys think?

It's nearly twice as long:

http://starwars.wikia.com/wiki/Resurgent-class_Star_Destroyer

2,915.81m

I heard someone say it's twice as long as an ISD. But we do have a spoiler thread where it might be better to move further questions and discussion, just in case.

wow, my bad..... did not get that impression from the movie