I have run my "Solis" system under various rules sets, first of all, it started as "Sidereal Traveller" and those pdf's were the initial incarnation; I found that someone already owned "Sidereal RPG" so here we are.
I am originally a CT player, circa '79; and I bought the '81 LBB's, bunch of other stuff. I mean, the first product I bought from GDW was Imperium, and also I played the Fifth Frontier War, Snap Shot, and Striker; as well as their Europa war games. Anything I play is probably in the vein of an updated CT, and there are some things, such as the LBB2 starship rules that I have come back to more than once because they are about the best. I have played Solis with CT, straight out of The Traveller Book, and I bought that because I didn't feel like bringing my LBB's to the tavern, to get pizza and beer stains on them. I also used MgT1 until the book fell apart from constantly have to flip to parts like skills. I also ran a game using M-Space, a BRP derived sci-fi RPG; was just emailing with the author yesterday, big plans, big plans. Nevertheless, I am also writing the second book of the setting, this is kind of the main course, where we played the games, sort of like a subsector book detailing two subsectors, which I call zones. I am also going to begin to run another tavern game, as well as pbp's, and a roll20 for Solis using CE, I use the rules in a generic manner, only a few house rules, such as no anti-gravity until up the tech tree, and no grav plates, or inertial compensation ever. Spacecraft are flip and burn; wheels and tracks are still a thing. I really look forward to get back to playing though, it has been a long time, months, and it feels like years.