[axsaxoman]

the next major jump forward in making the jp4 head flow better is a job for someone on an engineering/motorsport degree course maybe.

get a head --cut it up and remove the ex ports +combustion chamber in one piece --basically half the combustion chamber +ex ports

take it to your 3d scanner -- then redesign it with much larger ports +suitably thick port walls
go to your 3d printer and make one
go to your local foundry = GET THEM CAST FROM YOUR PATTERN
then weld these units back into std head-.

you could even cast them with dimples !!
I have wasted quite a few heads trying to get ports -especially on the ex-side larger --just not enough wall thickness in castings to make size they should be --smooth or otherwise.
I certainly would have done it when we raced the 8v --but that was long before scanners +3d printers+CAD programs to make patterns ,
I did make a totally downdraft head by having inlets remade and entering head at a vey high angle down side of spark plugs -- it made a difference ,but no one wanted to pay the cost of doing it that 1294cc 8v made 171bhp @8700rpm
getting totally new head castings made--simple enough ,just you need to make a hundred at least to make them viable
best performing 1600 cc will be the honda --just have a look one and you will see why the j4or jp4 heads will never compete with them .--