No krazy glue has worked great for my magnetization stuff. And the forgeworld terminators upgrade kit fits PERFECT with power armor in terms of scale. For some reason all forgeworld stuff I've seen is just the tiniest bit smaller than normal
GW stuff. I currently have one of the combi bolters attached to a mk4 assault marine arm and it looks fine.
This is it. I know it's not on a model but you can get the feel for how big they are.