Porting small block 915 j-heads

Hi guys and Gals,

Short Side Radius, what's the LOWDOWN on 'how far to go'?

Anyone got some flow bench info as I don't want to wreck a good set of J's by 'going to hard' at IT!

340 J floor waterway SSR info.jpg

This is a 'Weslake' J-head cutaway I found here in the UK.
As you can see the floor is limited by the waterway, but how far should you 'pull the seat' BACK???