Not meaning to offend class purists but I've noticed that the stern does have a substantial drag. Thinking about putting a scoop and through tiller for greater efficiency. Any advice ??

I suppose I'm a class purist. I don't quite see the point of doing these sorts of mods. There's no point in doing it for racing. You'll lose the option to go one design, and if you race PHRF, nobody is going to believe it wasn't a bad rating when you win, and who knows what to think about your rating when you lose. PHRF's a bit of a crapshoot in the best of times, when it comes to ratings, but at least with one designs, there's some hope of keeping skill out of the picture. Custom boats, tho, it is pretty hopeless.

In terms of doing it for cruising, well, sure, I suppose. But, structural mods aren't cheap, and you're putting them into a boat that's 20 years old. You're also going to eliminate a bunch of the resale value of the boat because you'll never sell it to anyone who wants to race.

Another reaction, for what it's worth, is that nothing's going to change the overall profile of the boat. It is a touch underpowered, especially in light air. You may squeeze a little speed out of the boat by tweaking the hull form, but that's not going to make a huge difference in that many conditions.

Your milage may vary, but it seems an odd thing to be looking at.

- David

Be careful that you locate the rudder at or very near to the existing location. The balance of the boat is based on the relationship between the rudder, keel and sail plan.

What you're talking about is a significant alteration. There are probably other changes that would produce more "bang for the buck". A possibility is changing to a bulb keel. A deeper heavier keel would allow you to more easily carry full sail into higher wind ranges without requiring gorillas on the rail. Another possibility is to add a bowsprit and fly a true asymmetric spinnaker.
That said, there are many areas where incremental improvements might be had. But all at some expense without any guarantees. For the era it was designed, the J30 is an exceptional design. If the J30 is not what you want, then you're better off buying the boat you have in mind rather than modifying a proven performer. Besides, you'll shoot a hole in your resail value if your mods cant be backed out. This boat's value is in its one-design capabilities. People would rather sail one-design than go two-tenths of a knot faster.

I'm certainly not a class purist since I only race PHRF but I would recommend against the modification described for all the same reasons listed in the other responses. You are looking at an siloated design element of the boat - Johnstone considered the entire hull shape, keel, sail plan, etc. when designing the J30 - modifying your boat would mean finding a like minded individual who belives in "innovation" like yourself. Likely you would find that people would shy away from your modified boat once you attempted a sale... I certainly would. One last BIG issue - I assume you race PHRF since you aren't a "purist." Your local PHRF guys will hammer your rating if you effect such a modification. In my area, it seems to be an annual ritual for PHRF to consider lowering the rating of the J30 - your mod would provide ample opportunity for PHRF...