E30 Zone

Hi guys,
In the e30 wiki m30 swap guide it says you can skim the b35 head by 1mm to increase compression.
is this upgrade that simple or is there more to it than the guide says?
thanks

It will change compression ratio as well, might need to use higher octane fuel as outcome to avoid detonation. Don't know what is safe limit of skim on this engine but gains will be close to zero by just skim alone.

Thanks, i thought it sounded a little too good to be true

I've heard many mixed reviews on this. Some people saying they had no problems with an easy 15ish hp gain, but some saying it contacted with their valves or didn't gain anything.