At the very least add gussets as a single row of screws/bolts aren't ideal for rigidity especially in T-sloted extrusions. That is if you stay with the current design. It may make more sense to change you design so that one extrusion sits upon another and then are joined with a flat plate
All that being said I'm not a big fan of using these rather thin extrusion for like this. It might be better to use a larger box section extrusion and put spacers underneath to raise the beam to get the gantry height you want.
Whoops didn't see that this post was old.
For kits I'm not sure what is available in Turkey. By the way your pics look great. Integrating a housing right into the design is pretty smart and should be considered for any dust producing router.
I love the "integrated casement design" add some insulation and you could get something really quiet.
Nice looking machine...great design. What is your cutting area?