Well, how would you lay out the map if you were me? I'm open to suggestions.
Pardon the super-crude art, it's just a sketch to illustrate the basic idea. If the UTR is the "setting" of the game, put it in the center of the map. Make the Recticulan state larger; you can allow it to off the edge of the map like in this example. This gives a very direct and immediate knowledge that they're the true power in the setting (or were) and the Terrans were something of a historical sideshow. Some alien race on the other side of the Recticulans won't matter in your campaign setting; just put the states in that will matter in your setting; immediate neighbors and those with some sort of role (like space nomads) that the players are likely to encounter. The nature of the Recticulans on that map also creates an immediate sense of mystery for anyone looking at the map: "How far does their state go? Who are their neighbors on the far side of their empire?" and I think mystery is very important in sci-fi games.
The other states in other colors are aliens; they're not all jammed up against each other; perhaps they only got star drive more recently, the Recticulans have "gate" technology in addition to Jump Drive to expand their empire more effectively, colonization is much harder than is assumed in Traveller, or something else has constrained their growth. This allows for true frontiers for each state to expand into.
Yes, there is a fragment of the UTR within Recticulan space; it's a part of the Terran state, probably some sort of historical artifact, like a lot of Terrans colonized there either by some accident of history or were settled there when relations were good with the Recticulans. Now it exists as a kind of "East Prussia" or "West Berlin" situation for the UTR; they can't abandon it for various reasons (perhaps the worlds are few but wealthy or technologically advanced or perhaps the worlds have some special place in the hearts of humans due to history), but it's a strategic nightmare for the present UTR.