Like Coffinmaker said, filler is not a good idea. I have been experimenting a bit with Titegroup. Its claim to fame is position insensitivity. While tests with extreme powder forward vs. powder to the rear reveal that it is (like all powders) susceptible to position sensitivity, I have found that it is much less so than Unique. When I'm not trying to position the powder in any particular way, and just shooting normally, I get much less round-to-round variation. But to accomplish that feat, it is a relatively fast powder. I have some "Ruger only" maximum loads that work well in my 4.75 inch Blackhawk when I'm looking for a consistent +1,000 f.p.s. loads out of it, but that is about the highest safe velocities one can get with Titegroup--and that is with a Ruger. I have tried a few loads around 6 grains in my Colt SAA, and I've found it to be a consistent performer but at the lower end of the velocity range.
The odd thing about Unique is, despite its powder position sensitivity and fairly high velocity variation, it remains a very accurate powder in the .45 Colt. I can't explain it, but my very best handgun groups were shot with 8.5 grains of Unique under a 255 grain pill out of a Colt New Service revolver. I know that my velocity spread from shot to shot can be over 100 f.p.s. with that load, but I still get a ragged hole in the target. According to your range report, you're getting good accuracy with Unique. If you want higher and more consistent velocities, give 3f BP a try. Compress 35 to 40 grains of BP in that case, and you'll get around 1,000 fps out of a 7.5 inch SAA and over 1200 out of most rifles. And if you've annealed your case necks first, your action will remain as clean as if you were shooting .44-40. And if you just want to stick to Unique, you may still want to try annealing the case necks. I anneal all my .45 Colt brass, whether I'm loading smokeless or BP. No sooty blowby on the case makes me very, and it keeps the action clean as well.
Thanks for the range report. I look forward to hearing about your progress.