Accurate Strong Gantry

[vargai]

Hello Everybody,

My target is to built a gantry for home use since I do office job and miss the miller work. (I have three sons so hope they follow the way)
The travel is 1000 x 700 x 250 mm with 1000 N cutting force in Plastic, AL, with 0,05 mm total accuracy.
After studying the relevant threads some contradiction still need to be solved.
I.e. my friend who build some CNC machines(not like this) says you only need one ball screw in the middle.
There are many ways but the proved, reported solution is my solution.
I hope with your help and skill I can reach my goal so please correct me where I am wrong.
Base is not finished in the attached figures.
My queries:

1. 1500 mm long rail position-side or top ?
2. Is there any good carrige pattern to eliminate the double ball screw?
3. At belt synchronizing version1 or version2 is the better? -my logic says the equal belt length in any drive direction give more accuracy .

Thank for your cooperation
BR
István