Strong? CNC

This is my first build. The goal is to have a relatively strong CNC to be able to cut alu.
As I don't own a workshop and sophisticated tools, I try to use very few custom parts.
I want find a compromise between a strong and a cheap machine.
Working space will be around 800x350x100mm.
For x and z-axis I will use the metal v wheels that roll on a square steel profile (see pictures below).
For the y-axis I use Igus linear guides (super strong, two rails and four carriges will be around 250$).
All axis with lead screws an two anti backlash nuts.
I didn't think about spindle and electronics so far.
Here is a close-up of the square steel profile and the c-beam. I will glue the steel piece onto the c-beam.


Update 05.09.17:
Today I got some Openbuild parts and I bought some cheap 6mm by 6mm square steel at the home improvement store. I made a small test assembly to see how it works:

it wasn't even necessary to fix the square rod as it is held in place tightly by the preloaded wheels.
For this test setup I used only four wheels (two on each side) and it already feels quite solid and the gantry runs smoothly. So the first test is a success. I ordered some better quality (stainless) rods for about 8$ each. With these it should even work better.
I don't have any plastic wheels so I can't compare with the regular setup (plastic wheels rolling in the groove of the beam).

I planned to glue the square rod onto the c-beam, but now i think this is not even necessary as the rod fit very well and is locked in place.


Now, as i pushed and pulled on the test assembly to get a feel for its rigidity i became unsure if it's really going to be rigid enough for decent aluminum milling. So might have to use more wheels...
More wheels mean more money. The metal v wheel assembly is close to 10$ each. So that will be around 100$ for the x-axis (8 wheels + rods).

I remembered some Igus linear glide bearings being very cheap (and probably more rigid than the wheel setup). So i gave them a shot and made an all glide bearing version of my build:



This setup will also be around 100$ for the x-axis.

Now, please leave your thoughts in the discussion section. Should I use the wheels or the glides? Thanks!