I have spent many years designing speakers
like you are trying to do now.
There is ALOT for you to figure out.
Efficiency, tonality and crossover matching
just to name a few obvious ones.
If you want to try it anyway be prepared to buy alot
of drivers that won't meet your requirements.
BUT when you hit on the right configuration
you will think it was all worth while.
Do the drivers have response graphs?
What is the fs of the tweeter?
Personally I prefer midwoofers with a slow drop-off
in the higher frequencies and just using a
GE Motor Run Cap to the tweeter.
I don't like inductors in a crossover that
drain the life out of the music.
Audax Aerogel and TPX are the ones I found
to work well in this configuration.
If you want to try a 4uFd for an 8 ohm tweeter
or a 6uFd cap for your 4 ohm tweeter.
BTW they call them MFD but same thing.
You can email me off line to contact me directly
to save bandwidth and time.
I have design software too that will help.
DanL
