I should note that I upgrade my HW starbase to have 16 construction yards. I don't believe I had a construction yard deficit in that game. The two starbases that my 20 colony empire contains have a combined total of 19 constructions yards I think. Thats almost one construction yard per colony.
Elliot: Do you recommend more than 1 construction yard per colony in a game?
No, I think a good amount is around 1 for every 2-3 systems or so. But it depends on a number of things: distance between colonies, how much cashflow you have, etc.
I centralise my construction in an attempt to minimise logisitics inefficiencies. In my experience it is resource availability and not construction yard availability that is the bottleneck. If I had one construction yard per planet the private sector would have to deliver multiple resource types to each and every colony. I think that a more distributed manufacturing network is therefore slower than a centralised one because less freighter trips need to be made for each resource type for the number of ships that can be built.
Resources are usually the bigger problem, but 288 new ships through 2 space ports is always going to be a bit slow
Your point about distribution is only true to a point: colonies with spaceports will only stockpile resources up to a certain threshold, so you're really better to just build space ports where it makes sense for your empire and then let the freighters ship all the resources around. As long as they're not getting chased away by pirates, space creatures or other enemies, freighters will keep all your space ports topped up. It does take time to move cargo out to remote locations, but if you plan to colonize that area then you are better off with a nearby space port anyway.
<b>Legends no longer allows starports to be built without a construction yard</b>
In RoTS I could build a spaceport without a construction yard as a stripped down base that every planet would have. I build stripped down orbital bases to keep maintenance low. Legends doesn't allow a starport without a construction yard. I have to make the starter base as a Defensive Base type. I still build all the colony improvers on my starter base, including the trade centre.
Do freighters still use my Defensive Base as part of the trade network to refuel? I noticed that when I build a starport the trade network lines get redrawn. Am I getting inefficient resource transport because I'm building the vast majority of my bases as the Defensive Base type?
Yes freighters will refuel anywhere that has fuel. But using only Defensive Bases will definitely impact things if you expect them to actually serve as space ports. They might do that in some respects, but much of the functionality will be lost. So I'd use a small space port instead.
The dashed lines between your systems are determined by your space port locations, but they are just cosmetic. Those lines have no affect on where your freighters will travel - they just show routes that will likely be well-used (because they join space ports)