i would skip the uv personally, buy a (vortex) diatom, i think you would be happier. i am still somewhat new to the hobby but haven't entirely seen the benefits of uv unless you are keeping very expensive fish....... it just doesn't seem to "do" much, and the expensive bulbs have to be replaced regularly i was told. i could see how it would help, but to me it just isn't worth the expense.
as far as flow placement, think currents...... point it towards the glass in such a way as the return path comes back towards the inlet. some sort of circular pattern seems to work best for me.... across the top, deflect off the glass and back along the bottom.
good luck