jdm 2008 model ej207 - I'm after info to help plan a refresh/build.. any knowledgeable peoples out there?

So I have a bad influence living a few houses away who's building his m235i bmw - and I felt that it was about time to start investigating "refreshing" the engine in my 2008 sti grb hatch. I've got around 300kw atw at the moment (winter temps rock!) - but i want that to be more, of course - and bulletproof - I'm aiming for a a nice 400kw atw build.

Is there anyone on here who knows those ej207 w20c block subi engines well? or can offer info about them at all?

I was halfheartedly looking up stroker kits for the engine and altho they do seem affordable-ish for a car that still does street driving, I'm not really wanting too much insanity, so I was looking at doing pistons, rods, springs, retainers and cams to go with what its got already.

The w20c block has 13mm cyl walls and a semi closed deck design - does anyone know how much you can bore out of that safely, or do you need to sleeve it if you want 1mm oversize pistons in it? it doesn't look like it runs a liner in any photos I've seen and the cylinder walls are by far the thickest I've seen in a factory engine for a while... (pic : https://jmms.co.nz/cdn/shop/files/2_48a4d007-7c1d-4972-b13d-f8a9f1049cb3.png)

For an eventual goal of 400kw atw - should I close deck it with inserts or would a couple of cm's of epoxy around the top of the cylinders do it ok?

...or would it not even be needed with the semi closed deck design it has? (see pic above)

The existing ej207 crank is already nitrided and depending on where you read its also heat treated and maybe induction hardened so I don't see a need to change that for my goals. It would be nice to have this confirmed as the spec however.

Pistons and rods I was looking at getting from the builder of "Gobstopper" (if you know, you know) Roger Clark Motorsports - his rods and pistons are totally excessive for my needs - proven in his cars - and very affordable - as is the stroker kit he does - but I was tending towards keeping the existing crank as I want to retain the factory 8k rev limit.

...Or does anyone know if a factory 2.5 crank would live under 400kw atw after being heat treated etc? Their 2.1l stroker kit with all the bottom end gaskets and seals etc is stupid cheap...

I've heard a few places / sites / youtubes say that subaru engines dont reeeeealy like high compression - is that in general due to design - or is that under boost with factory rods or is that due to people who have done it getting a bad tune or something? Anyone heard anything like this and has knowledge around this?

Anyone here know or have heard much info/anything about the nitto ej stroker kit? Nitto said its got the potential to hold up to 250hp per cylinder which they have seen on a race engine before - heck - I'd be happy with a "mere" 150hp a cyl :D Their GTR stuff has a good reputation in Aus, they have Evo and Nissan SR stuff in the wild - but I've not seen the EJ stuff out there anywhere.... Any links to anyone / vids / workshops that have used it before? It costs more than the RCM one - but they have their own forged crank - and its still "affordable" but I don't really want to be a guinea pig...

Any info from anyone who has knowledge not theory's I'd be very keen to hear from please - I know enough to say "i dont know" and so...."Hi everyone, I have questions :D"