Dome Question

[incognito]

Curious what people's dome layering strategies look like... Answers should address things like:
a) how many gems to put into a single dome... this seems to be a trade-off between the dome shattering soon anyway from enemy spellcasting and the cost of recasting
b) which domes you like and why, and the order you layer them
c) typical timeframes for installing domes. Clearly part of this answer will be when people start casting spells at my provinces, but by now, most of you have a sense for when you should have a dome up in any given MP game
d) drawbacks/tips/tricks with domes - things like don't try teleporting through your own dome (surely there are more)
e) specifics for domes beyond the manual. Take for example the blood magic dome (astral corruption? methinks). The manual description warns that those casting spells into it may be feebleminded or some other vagary. Does this happen or is it just an erroneous description? Also it warns that horrors occasionally attack mages within the dome. How often does this happen? Feels like an important thing to know before casting such a spell. And that's just one example...

As always, thanks in advance for the great answers.