1992 Palma Match ammo was done on the somewhat beefier 1050, but it can be done on the 550B. The only modification to the normal procedure I would make is to buy a Redding Competition Seating Die. These dies go a long way to making up for bullet runout error due the press not being a Forster Co-ax or an arbor press setup (both of those arrangements allow dies to find their own center on the case). That runout error can be seen on the target and accounts for up an moa of error in the bullet size you are using.
Regarding the powder measure, I think you can make it work. I found it helps to add a second baffle perpendicular to and a couple of inches above the molded-in one in the Dillon measure. You can download my .PDF file of baffle templates and instructions
here.
Hatcher tells of selecting powders for National Match ammo one year in which candidates had been narrowed to a stick powder and a small grain powder (this was between the World Wars, IIRC, so it preceded spherical propellants, if I have my memory and history right). The armory's loading gear would hold the charge weights of the fine grain powder to within something like a .6 grains extreme spread, while the stick powder could only be held to something like twice that. Nonetheless, the stick powder consistently produced more accurate ammunition regardless of how they adjusted the charge. Hatcher attributed this to the superior ability of stick powders to light up consistently.
I have pulled bullets on match ammunition and ball ammunition in the past to measure charge variance. The best was Winchester Supreme .308 match ammo with 168 grain boattail match bullet. It had a minuscule 0.05 grain extreme spread in its very fine grain 748-type powder. By comparison, the Federal Gold Medal .308 match ammo with that same bullet type had a 4895-like stick powder with 0.4 grains extreme spread. Nonetheless, the Federal Ammo shot better in my guns.
So, I expect you will find Reloader 15 has pretty fair ignition and can tolerate a bit more charge variance than some other powders. I wouldn't worry too much about it. If you feel you just have to get the best possible automatically operated volumetric charge metering of stick powder, the
JDS Quick Measure with its Dillon adapter will stay within 0.2 grains even with a fairly coarse stick (probably within 0.1 grains with something as fine as RL-15), but that's an investment and you probably won't have time to get it and mess with setting it up by Saturday. You do have the option to weigh charges and pull the Dillon measure and drop the weighed charges in through a powder funnel.
I don't know if you have time to do any testing? If the load is a good one and you know it will tolerate some charge variation, you should be good to go with what you have except getting the competition seater. Add that second baffle, though. If you want information on how to find loads with wider charge tolerance, check out Dan Newberry's
OCW load site.