What Stu said.
I prefer having block-and-tackle adjustment on the traveler car. On our Raider 33 we had a 2:1 system; it was patently inadequate. I use to play it in and out during races to control heel angle; it did not slow the boat down when on the wind.
I built a bridge deck on my H25 for the traveler but have not found the funds to buy the Schaefer one yet. Since I planned this, Schaefer changed the old system to one with cheesy-looking black alumium plates under the control blocks instead of the nifty little cast-stainless 'track slides' that mounted at the ends of the track. No one is selling used ones on eBay. So I decided to make my own.
You can do this too, avoiding buying Garhauer stuff or anything else. Just get two double blocks, or double cheek blocks, which are better, and mount each one on a little plate of aluminum or G-10 (don't use any other metals; of course Starboard is insufficient for this). You can buy the Schaefer ones to match the rest of the boat or the ones at Dwyer Aluminum Mast (DAMCo), which look just like them and are cheaper. Mount these at the ends of the track-- just drill right through the blocks' pins and into the track-- and through-bolt these. The most important part of the backing block is at the ends of the traveler; make these bolts go through that. Then-- only then-- play with the control line and decide where you want to cleat it.
This is the biggest oversight in tackle-controlled traveler adjustments. Some people put the cam cleats vertically on the coaming, some horizontally, some on the deck/cockpit seat-- it all depends on who's going to be doing it and where he wants to sit. But the options are wide-open, since you don't have anything at all now. You might consider running them right back along the whole inside of the coaming (through bullseyes of course) to the back where you can reach it from the wheel.
The great benefit of control lines is that these, not the mainsheet, are what you need to adjust more often, and to greater effect, than the sheetline itself. This will prove self-tending in most cases, allowing you a very smooth way of going about, even if your two tacks are not at the same angles off the wind. Leave the sheet alone and just ease or trim the traveler lines. For this reason I would advocate not less than 3:1 control tackle on your 30-footer and suggest 4:1 (if you have the traveler-car sheaves for it).
Your move to 6:1 on the sheet itself is good. Mind that old fuzzy line will negate some of the benefit of having new blocks though!
On our Raider we had a double-ended sheetline, something my dad tended to draw for every boat that had a traveler at all. We had Harken ball-bearing rachet blocks, the lower one having a cam cleat. That was one end. The other end went up and ran forward under the boom, down to the mast base (there is no other point on the deck where this will work) and back along the deck to the winch at the hatchway. The cockpit end was for racing dinghy-style and in light air. The winch end was for heavy air. Of course you need a really good line stopper on the deck for this!
As an added feature, the mainsheet leading at a 45-degree angle down from the boom to the base of the mast precludes the need for a vang (yes. Really). We used our vang as a preventer instead. I won't do this on Diana as I don't have the winch room for another line on the cabintop; but I did consider it.
It's all up to how you want it. I would only strongly suggest that you decide how you want it first and then go looking for the hardware to make it happen. Hardware retailers love guys who come in not knowing just how to rig something. When I sold (almost said 'taught'!) at WM, I always tried to educate the guy first, then ask him how he wanted it now that he knew something. But most retailers won't do that; and of course online you won't even get a person.
Do let us know how you make out with this!
