Looks like you're using a 200 or 250RNFP.
Titegroup, Clays, W231/HP-38 in that order. Skip trailboss, it's a waste of time and money, it's expensive and you only get 14oz per jar (that's all that fits). I really have yet to see any circumstances where trailboss does anything better than any of the other powders out there, dealing with cowboy ammo for so many years, I've seen and been asked to use tons of the stuff and I've come away with a pretty sincere distaste for it. For a 200gr, RNFP, go with about 5-5.5gr of Titegroup, it's a pretty mild load and has always performed well, Clays is about the same, but with the higher case volume it doesn't always burn as clean as TG does, again, you're in the 5-5.5 grs range. W231 is a bit hotter, but you're going to need to be in the 6-6.5gr range to get decent performance.
It's worth noting, none of these are going to fill the case to your 55% mark, but they are all safe ranges and have a long history in the production of factory ammo in this caliber.
As usual, these are all mousefart rounds the SASS shooters like. if you want something with a bit more punch you should be looking to HS-6 or Bluedot. Unique is going to really be too slow to work well unless you're shooting it in a rifle. Oddly, I use Unique to load 45-70 on occasion. Works quite well actually, probably better than it would in .45 Colt.
I would defer to the advice of Mr. @AMProducts ! Always appreciate your input. I only brought up TrailBoss because I had wanted to try it in .44 special to get a fuller case and full clean burn. I haven't seen Trailboss on shelves locally for three, or more, years, though I haven't really looked for it for some time.