I've had my OT, which is chambered for 44 Spec since 2008. The first several years I had it, I loaded and shot 200-240 grain wheel weight lead cast bullets using Titegroup (which is an excellent smokeless powder) and Trail Boss (also good) in 44 Spec. I also loaded and shot 44 Colt, starting out with 25 grains of Goex FFF using a softer lead Lee cast bullet, but then switched to using 25-26 grains of Goex FF using a Mav Dutchman 200 grain soft lead bullet. Kept all smokeless in 44 Spec and black in 44 Colt brass. Much of what I read stated a "more harmonious outcome" could result using FF over FFF in a gun such as the OT. Good accuracy with this load, not a hard load on the gun or excessive recoil. After the first several years I quit shooting 44 Spec smokeless and just shoot the 44 Colt FF black in it and a Richards II. I have loaded and shot 44 Spec using the Mav Dutch and FF black, works ok, but no real advantage in target shooting.
You want to stay with the milder loads with the Open Top/Conversion style Colts when using smokeless and not use any powders or grain weights that develop high peak pressures rapidly as Hodgon advised. I've never used Clays in any of my revolvers, other than early loading of 44 Spec using Titegroup and TrailBoss, I have used others in the same general burn rate as Clays such as Red Dot, Win 231, Unique, 700X, PB, and HP38, but these are just loaded and shot in top strap modern day revolvers such as Rugers. Have used them in calibers such as 45 Colt, 38/357, 44 Spec, and in 45 acp(1911 Colt). I've been going to cast some 240 grain soft lead bullets in the Lyman mold I have and load them in 44 Colt brass using FF and try them in the Open Top and Richards II, but haven't done so yet. Did Hodgon say not to even use the milder start load with the OT? The open top frame is weaker than the top strap version, could be they don't want reloaders to get carried away with loads that result in firearm damage and shooter injury-the liability thing.