It will only close the door on backyard settling if we keep the entire ring of cities around the ring...
Maybe we can do just that? Keep a city on the outer ring just to disable landing of settlers? I think that can be done easier...

If we put a few Frigates on the Yellow lines we effectively cordon off the outside....
Add one or 2 near BT which we need for protection there anyway... and our "backyard" is protected.
Before declaring on Germany we need some more Frigates in/near BT to hold off Bismarck's fleet from disrupting our cities there ....
Food for thought...
- Is it worth building a Drydock (180 hammers) to speed up (and get +4xp) boatbuilding in either Madrid or Barca?
A Drydock we get 100% bonus for beeing aggresive so thats actually 90 hammers.
In barca we get 10 extra hammers on boats, so if we spend 9 turns building boats we break even... 9 * 35 (hammers per turn) = 305 / 135 (Frigate) = 3 Frigates...
In other words, if we plan on building 3 or more Frigates/Galleons ... It is to our "profit" to build them from a Drydock in Barca.... We get more XP and spend less hammers.
I think we need no more Galleons but Frigates? Dont know...
- is it worth investing 17 turns for Westpoint in Osaka? Maybe a little less with a timed whip (overflow) and some chops?
With westpoint we have 10XP units (CR3 Samurais, CR3
Pikes! or CR3 Cannons I think ) comming out of Osaka

We are however investing 17 * 47 = 799 (raw) hammers (or ~6 Cannons/Grens, or ~8 Samurais), On westpoint we get a bonus with stone... therefor the number of invested hammers (799) is lower than the hammers needed to build it (1200).
- Is it worth investing 23 turns in Ironworks in Osaka?
We are investing 1050 hammers (no bonus) to get 50% gain later on...
50% gain is 15 hammers 1050/15 = 70 turns to "Break even"
- Is it worth building both Iron works and Westpoint in Osaka?
I am only considering Osaka at this point but if anyone have any other suggestion please do suggest...
Edit:
Another suggestion... Build only (cheap) Pikes (they get CR!) and Crossbows (No CR) in Edo and Kagoshima these upgrade to Grenies...
LBs are also possible to replace the current garrison of the captured cities which are now (offcourse) garrisoned by Grennies/Sams and Cats
Pike or Crossbow => Grennie = 200 gold
Samurai => Grenie = 155 gold
So at the current GPT (+465) we can upgrade 1 Pike and 1 Samurai every turn without every capturing a city and still run a surplus
Edit2: At 47 hammers (+100 gold) per turn (currently) Osaka can build us a Pike every 2 turns

,
Thats is a CR2 Grennie every 2 turns

(without Westpoint)
I dont know why we/I didnt spot that earlier
