TradeRoute2 LargeMap

I hope you've played the large stock map Twin Empires already - I (RedKnight) was pleasantly surprised to see that all the wormholes went somewhere "man has never gone before". Or, at least, I hadn't, nor the AIs, before I dusted them all. I figured they just cut back into the map at crazy angles but, lo and behold, there were new worlds there - not connected to any star.
This map has symmetry plus a lot of wormholes, which make for an extreme example of a long trade chain. If you ignored the spoiler alerts - remember to listen to them, next time. It's a fun map for discovering new things.
= Good Chain =
== Example ==
Here's the most extreme trade chain I've seen, outside of mod maps made for optimizing trade chains. An alternate design with the same number of jumps is shown in the thumbnail:
By tactically not making Trade Ports at the planets marked with X, you make more money by making less trade ports. There are 36 planets that could potentially have TPs, but only 28 have them. (There are 8 X's.)
Planets with a Y were irrelevant to the chain - and therefore got a trade port. In the two examples on this page, there is only ever 1 trade port per planet that can have one (if it does), to keep things simple. This happened to be a great map instantiation for testing (not playing!), because there was only one trade bonus to muck up the numbers (see Spam, below).
== Math ==
Let's do the math, as for the simple Centrifuge map:
*Game Income Rate is Normal (+15% vs. Slow values listed in most parts of this wiki)
*+30% Trade Income research (Vasari)
*28 trade ports ... 24 are in the chain, plus there are 4 marked with a Y 
*Long chain number of jumps: 34 (even though only 24 ports are in the chain! gotta love UCGWs)
For individual trade ports:
 = Rate * ( ( 1 * Research ) + ( .075 * Jumps) ) 
 = 1.15 * ( ( 1 * 1.30 ) + ( .075 * 34 ) ) 
 = 1.15 * ( 1.3 + 2.550 ) 
 = 1.15 * 3.850
 = 4.4275
28 * 4.4275 = 123.970
= Spam Chain =
== Example ==
Here's the same map, but now every planet that can have a trade port, has 1 TP. That's 36 TPs in total (the 8 planets with Xs above got TPs): 
Notice how much shorter the longest trade chain is; it went from 34 to 12.
== Math ==
 = Rate * ( ( 1 * Research ) + ( .075 * Jumps) ) 
 = 1.15 * ( ( 1 * 1.30 ) + ( .075 * 12 ) ) 
 = 1.15 * ( 1.3 + 0.900 ) 
 = 1.15 * 2.200
 = 2.530
One of the new planets (Caldeira) has Pharmaceutical Flora, making its income 3.036 (1.2 x 2.530).
36 * 2.530 = 91.080
Plus the extra 0.506 (for Caldeira) gives 91.586.
= Comparison =
The spam map has +29% TPs (36/28), but makes only 74% as much income (91.6/124.0). Individual trade ports are only making 57% as much (2.5300/4.4275). If you weren't watching your chains, you would have thought +29% on top of 4.4275 per port and 124.0 total would equal 5.6925 per port and 204.93 for all 36. But instead, you make 91.6 in total - less than half of the "superficial" projection - even though you paid 29% more.
Conclusion: If you have a big map that allows for long chains, be very careful of where you put your TPs.
For the record, maps with a lot of stars and few planets will never support long chains... the stars "short circuit" any long chains, since their planets are close. But hand-crafted maps like Twin Empires, with one star, lots of symmetry, and some wormholes built in, can allow some very long trade chains.