I just realized that it might be easier than we have ever thought to use CT characters with T5.
My Current Way
My current way is to map skill levels, because in T5 you get more. I went into The Traveller Book and analyzed the special rules for each skill, and grouped the skills into an "A" list and a "B" list.
Now I mapped skill levels from CT to T5. First, I doubled the CT skill level, and then, for "A" list skills, I would add one more.
What you end up with is a "close enough" system.
My New Brainwave
Consider T5's task system. It has that special TIH rule that says if your skill level is lower than the task difficulty, you bump up difficulty by +1D. On the average, that's similar to a -3.5 DM to the task.
So how about using CT characters just as they are, and dropping TIH?
Consider the bloke with Dex 7 and Gun Combat 1. Assuming NO MODS AT ALL, at Range 2, his chances are better than CT (68%):
2D < 8
At Range 3, again assuming NO MODS AT ALL, his chances are low but not unreasonable (26%):
3D < 8
This is when ignoring TIH. This also ignores a number of possible difficulty and dice modifiers.
Summary
It's easier to run CT characters in T5 by not mapping skill levels and ignoring TIH. You, as referee, always have to be sensitive to the player characters' skills mix, skill levels, and general capabilities, regardless of system. This kind of sensitivity PLUS throwing out TIH for CT characters makes them work AS IS.
My Current Way
My current way is to map skill levels, because in T5 you get more. I went into The Traveller Book and analyzed the special rules for each skill, and grouped the skills into an "A" list and a "B" list.
Now I mapped skill levels from CT to T5. First, I doubled the CT skill level, and then, for "A" list skills, I would add one more.
What you end up with is a "close enough" system.
My New Brainwave
Consider T5's task system. It has that special TIH rule that says if your skill level is lower than the task difficulty, you bump up difficulty by +1D. On the average, that's similar to a -3.5 DM to the task.
So how about using CT characters just as they are, and dropping TIH?
Consider the bloke with Dex 7 and Gun Combat 1. Assuming NO MODS AT ALL, at Range 2, his chances are better than CT (68%):
2D < 8
At Range 3, again assuming NO MODS AT ALL, his chances are low but not unreasonable (26%):
3D < 8
This is when ignoring TIH. This also ignores a number of possible difficulty and dice modifiers.
Summary
It's easier to run CT characters in T5 by not mapping skill levels and ignoring TIH. You, as referee, always have to be sensitive to the player characters' skills mix, skill levels, and general capabilities, regardless of system. This kind of sensitivity PLUS throwing out TIH for CT characters makes them work AS IS.