Last week I installed new wedges in my partners. I got two packs of about 20 each recycled wood-plastic composite construction shims from Ace Hardware. I made wedges of varying thicknesses as needed by taping them together. The shims come with break spots so you can snap off the excess below and above after you're done. I have a package of Spartite waiting to use but was in a hurry so I got these shims for about $4 per pack. Don't think the Spartite is going to be used!

I used the Rig-Rite continuous rubber mast wedge on my C34. It was a good product, but it was compromised in my application because the vang attachment in the mast track was too low to the deck to allow the wedge to fit properly there. So I had to position the joint there and caulk the heck out of it. It did work, but check fit issues before you buy.

When I pulled the mast, I replaced it with Spartite, which was perfect.

After a rigger put some in which failed, I used the Ace Hardware shims, per what Nick says above.  I put a large hose clamp around them to hold them in place when the mast bends over one way or another a few millimeters.  Cheap and effective so far. 

Have tried several ideas but I haven't yet found an easy, effective way to stop the rain drips though.   Does the spartite take care of that?
 

What I have done as far as the boot is use the silicon rubber tape that fuses to itself without glue. I first use the clamp at the top and bottom than use the tape around the top and cover the clamp. The bottom is optional and needs to be removed at haul out when they remove the mast. The boot is stored on the mast so I do not undo the top. Where the boom vang attaches at the bottom I use silicone to seal and keep the rain out.

Call me crazy, but I'm wondering if wedges are even necessary?  If your rigging is tensioned properly including (on my '91) the turnbuckle inside the cabin connecting the mast just below the deck to the fitting in the ceiling and your boot is flexible, even under heavy conditions the bend in the mast at that point is going to be minimal, and even if it reaches the side of the through-deck fitting (which would be very tough given the turnbuckle tensioning the mast aft under the deck) it seems to me that a half inch+ of flex is merely going to pull the boot around a bit? 

Note re: through-deck leaks: my solution to the leaking around the boot was to undo the two hose clamps top and bottom, slide the boot up about 2 inches and put a thick bead of silicone around the mast at the point where the top of the collar sits normally, then slide the boot back down and reclamp it.  The silicone is flexible and easy to remove/scrape off, and with a bit more on the bolts holes that attach the fitting for the vang, I largely eliminated the leak. 

HOWEVER, in certain weather conditions/temps there is a lot of condensation that builds up inside the mast collar due to the aluminum mast being cold below deck and the sun heating up the white rubber boot.  To address this I bought a can of the white water-based expanding foam now available at most big box and small hardware stores and filled the entire space (again, I am not using mast wedges, perhaps foolishly...) with this foam.  Once it dries overnight, I just used a sharp knife to trim the underside flat against the ceiling.  No more condensation or leaks, and the water-based foam simply scrapes off cleanly when I lift out the mast with the crane. 

The turnbuckle on the inside of the boat is to prevent "oil-canning" of the deck, not to stabilize the mast in the partners.  Three major reasons for wedging:

• Without the wedges, the distance between the spreaders and the mast step is such that adding additional rigidity along the span is desirable.  Adding rigidity to the length of mast between the base and the partners help ensure that the mast butt sits squarely in the mast base and therefore does not put localized strain on any edge of the mast butt.
• In almost all most boats, the amount of mast flex at the partners during high rigging loads will cause the mast to bear on the partners, causing excessive localized stress here too.  Usually the forward edge of the mast will bear on the forward edge of the partners due to the mast driving the boat forward during high mainsail loads.  In some cases, the hole in the deck and the position of the step are such that one side of the mast will rest on the partners.  Wedges tend to spread out this contact area.
• Finally, wedges immobilize the mast and make sealing the gap (theoretically) easier.

I went for years without mast partners (wedges or whatever). I couldn't see a reason for them.  

When I started racing I brought in a rigger to look over my setup.   He said the same thing Nick says above.  The decrease in mast bend after the wedges went in, made the boat point better upwind in addition to reducing the "point-loading" on the base of the mast.  Once I understood what the rigger was talking about (and he had to draw it out on paper) it all made sense and I realized that's a lot of pressure on one tiny spot.

I got cheap (but strong) plastic shims at Ace Hardware (on someone's recommendation on this forum - another post).  I put them in from the bottom and then put a stainless steel band clamp around them to keep them from falling out when the mast tries to bend.   Works great so far.