Just tried this and I'm not sure it's made a huge difference tbh. My gap was nowhere near as bad as some other examples I've seen though, so maybe it's just diminishing returns.
On the plus side, I didn't have to remove the bumper...just undoing the side indicator and taking a clip out from there I was able to pull the bumper forward enough to fit this clip. Very fiddly (the clips are tiny), but managed it. Im not going to do the drivers side...it wasn't as bad, and now they look roughly even. It just looks like "bad panel gaps", rather than "bumper falling off". Stupidly, I forgot to take a 'before' picture, too.