Hey Pudding and thank you so much for sharing your thoughts!
First and foremost, I should have mentioned I'm driving a MK2 Leon Cupra R. The current suspension modes I installed are Powerflex black series anti-lift kit, Hotchkis rear anti-roll bar and Wavetrac LSD.
Bracing - not required in the MK5.
Are you referring to strut bracing or Unibrace? To my understanding, RedRobin's review was very favorable to installing the XB & UB. However, for the LCR, there's only UB.
VWR dogbone mount (it's actually a Vibratechnics part) - It *does* increase noise and vibration. You need to do all 3 to keep that motor pinned, but the noise and vibes are horrendous if you do so, even with fast road spec rubber.
Indeed, that's my understanding as well. And since my car is first and foremost a daily driver, with the occasional tracking, I want to keep it comfortable enough so my kids don't complain when I drop them off to school
Polybushes - Yep, the anti-lift kit is worth doing.
I have the Powerflex black-series anti-lift kit installed.
Leave the rest of the chassis bushed with rubber, refresh with new OEM parts if necessary as fresh rubber is better than 10 year old rubber.
Interesting. So in your opinion poly bushes won't make much of change, compared to relatively new fresh and OEM rubber bushes?
No worries, just my experiences, not facts
Strut bracing. Bear with me......
I tried the Unibrace stuff in my MK4 R32 and it made a moderate difference. It wasn't like "Wow, that was £150 well spent"!
Now, the MK5 is apparently 120% more rigid than the MK4. Normally a successor is around 40% more rigid than it's predecessor, so 120% is a huuuuge difference. I can also just 'feel' the car would not offer huge gains by bracing it. One tell-tale sign of body shell rigidity, on a 3 door especially, is when you jack up one front corner, can you open and close the door smoothly on the jacked side? On the MK5, yes you can. On the MK4, no you can't! That is major chassis flex!!
By all means, try a rear brace first and see what you think. If it feels like you've gone up a size in rear arb, then the car is benefitting from it. If you can barely notice anything, the car is rigid enough! Having said that, I don't know how rigid the Leon is compared to a Golf.
Dogbone mount - I'm fortunate enough to be able to compare a bone stock GTI to my Edition 30 and I can 100% promise you the uprated part transmits noise and vibes into the cabin. Not massively so, but you do notice it, especially in the daily traffic grind. I am very picky though, so may notice it more than others do. It does remove a bit of slop, but nothing like as much as doing all 3 mounts does.
Polybushes - Hmmmm, not my cup of tea personally. Maybe the softest grade of poly might suit some people but every time I've used them in the past, I think great at first, and then I hit an unfamiliar road and there's some noise and vibrations I wasn't expecting. I've always found refreshed OEM rubber to offer the best compromise.
I should add all of this is based on a road car. Track weapons would benefit more from these kind of mods but when using the car in both scenarios, there is always a compromise to be made somewhere. Some folk are happy to compromise, I'm less so :)