the 9.8:1 piston we carry is not forged, it is cast. couple things to consider here , and let me preface this by saying this is a good bit of my opinion.
if you have unlimited funds or a good sum of money at your disposal, get forged rods and a custom compression ratio above 10:1. you will need to go to premium gas, with or without tuning, and generally to get the most from this you'd want some head work if not cams as well.
cams are more important here than head work. Bigger cams will make up for SOME of the lack of flow in the protege head. At the end of the day there isn't a great deal that can be done by porting alone, and imho, oversized valves on all but the most REDICULOUS NA motor builds with the FS is going to be a waste of money. Reason why cams are critical? you can push larger overlap and bigger duration without compromising dynamic compression, because of the higher static compression. It would be more correct to say high compression pistons compliment/allow for bigger cams, than to say cams compliment the pistons - the pistons will work regardless - but large overlap cams with big duration will struggle if the compression isn't high enough.
As for cost - In my experience with wiesco and CP, custom pistons are not greatly more expensive than their off the shelf varieties - the biggest pain is the lead time to get them made. There are also other advantages to going with custom pistons, namely larger wrist pins (which of course would require a new set of rods - i'd recommend a set of forged long rods - the stock rods simply will not put up with absolutely spastic engine speeds, because the forces at play get absolutely insane when you start winding the engine up - we're mainly talking about piston accelleration here, the force that can and WILL cause rods rated to support 400hp on a turbo application fly apart at 190hp on an NA application - with spectacular results).
if you've got the money for it, spend it. horsepower achieved is directly proportional to dollars spent
Truer words were never spoken - unfortunatly to get any sort of REASONABLE joy out of the FS all motor, you have to open your wallet. Its not a honda motor that can see tremendous power gains from the simplest of bolt ons. You as well as anyone know, the engine lends itself to turbo charging more than NA - the VERY poor rod ratio, relatively long stroke and massively under-square cylinder design is great for holding back the deto and running big boost, but it works in every single way against anyone who is serious about running a number on an NA motor.
if you don't have a lot of money to spend but still want a nice bump, keeping your stock rods and going with Jspec or our pistons will work fine. couple those with a set of cams and at some point some kind of tuning, it will be a definite improvement over the stock FS motor any day of the week. we can talk and debate all day long about the best route and best parts, but be honest with yourself first about your budget and your overall goals before making the plunge.
You are right - we have no idea what kind of goals he's after here - i'd hazard a guess though, that 170, MAYBE 175hp would be the most you could expect from JDM pistons...and you would need something better than j-spec cams. Maybe its just because here Australia we're spoiled with higher compression pistons and JDM cams stock - a move for us to JDM pistons is nowhere near enough to make it worthwhile. My argument is that you've got the motor torn down, you're only going to want to tear it down ONCE - you might as well spend the dollars and build something that is going to be reliable, and support the most amount of power you can live with before driveability becomes an issue. I'm not saying everyone should go and invest tens of thousands of dollars in building a 200hp 9000rpm grenade - but the LITTLE (and it wouldn't be a great deal) bit of money spent while the engine is down, on custom pistons, forged long rods, and cams with a decent profile will save you the "I wish I did this better" in 3 months time when 160 whp becomes boring........
Mind you, it sucks owning a NA protege...theres really NO decent headers available, theres no decent IM available, theres no decent rod and piston kit available...unless you want to spend big dollars you're stuck with stuff that is really not fit for purpose...*sigh*