I aint no expert, but ill do my best answering the questions i found in http://www.angel.ne.jp/~france/EU/maps/8.html
I agree with you and alvaro that san sebastian should be euskadi's city, but euskadi should of course be named 'País Vasco' and not vascongadas.
I think that if you're gonna name north castilla 'Castilla la vieja'('old castilla', the name it had when Franco was the boss), then southern Castilla -actual name:Castilla La Mancha- should be named 'Castilla la nueva'('new castilla', name it had when blablabla). Another solution is to give the actual names, ie Castilla La Mancha and Castilla León. Anyway in that period it was just 'castilla', so you could just name it north and south castilla
No, i dont think the mountains there in extremadura could obstruct much armies. I can tell, ive been living there for some years.
About sierra morena: i dont know what to say, because it depends. From Andalucia's side it may be pretty impressive, and hard to pass, but from castilla they are like a depression, because Castilla's like suspended and in a plane, if you know what i mean. I think you do, cause you wrote that first you were going to make castilla a mountainous region and now with the mountain rule you dont need to.(at least martin knows what im talking about.. or not..
)
I dont think valencia and catalunya should be separated with mountains, instead, you could use the ebro as frontier and partition aragón as martin wrote
i dont know what to say about the balears.. they certainly are pretty low, but you cant put a desert or a plane either..
I agree with all the other propositions, and think you're doing a great job. The original map -not yours, the ones ive seen on screenshots- werent good at all.
Keep on doing such a good job!!
PS
erhaps you could put the national names-not statal- on EU2?!? 
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River styx condominiums, rectum dominate
I agree with you and alvaro that san sebastian should be euskadi's city, but euskadi should of course be named 'País Vasco' and not vascongadas.
I think that if you're gonna name north castilla 'Castilla la vieja'('old castilla', the name it had when Franco was the boss), then southern Castilla -actual name:Castilla La Mancha- should be named 'Castilla la nueva'('new castilla', name it had when blablabla). Another solution is to give the actual names, ie Castilla La Mancha and Castilla León. Anyway in that period it was just 'castilla', so you could just name it north and south castilla
No, i dont think the mountains there in extremadura could obstruct much armies. I can tell, ive been living there for some years.
About sierra morena: i dont know what to say, because it depends. From Andalucia's side it may be pretty impressive, and hard to pass, but from castilla they are like a depression, because Castilla's like suspended and in a plane, if you know what i mean. I think you do, cause you wrote that first you were going to make castilla a mountainous region and now with the mountain rule you dont need to.(at least martin knows what im talking about.. or not..
I dont think valencia and catalunya should be separated with mountains, instead, you could use the ebro as frontier and partition aragón as martin wrote
i dont know what to say about the balears.. they certainly are pretty low, but you cant put a desert or a plane either..
I agree with all the other propositions, and think you're doing a great job. The original map -not yours, the ones ive seen on screenshots- werent good at all.
Keep on doing such a good job!!
PS
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River styx condominiums, rectum dominate