A cpu oc'ed to 4GHz @ 60c (w/load, idle?) it just seems a little high thats all.
I cant give you an accurate answer as to why 60c seems high to me, not enough info, but if your ok with it then we...

Wow I would say that your the exception.. good for you. Because I would bet that most people who have made the mistake of using a shop air compressor thats not properly set up to blow out a pc...

60c yikes! I guess It's time for an upgrade.. jk :p

IMHO I'd Just spend the extra $30 for the H150I Pro. 360mm rad with Triple ML Pro series fans(Mag. lev.) with zero rpm speed at idle temps.. I mean whats not to like about being quiet or even...

Never use a shop air compressor! they are not pc hardware friendly. If you do want to use one you would need to install two parts on to the air compressor..
first: A psi(pounds per square inch) to...

"It was just a question of radiator position at the bottom of the case, not about hoses"

[Quote OP] "does anyone know if its any downsides by placing a radiator horizontal, with the tubes...

Sorry but that's not correct, an aio's radiator and hoses can be mounted in any position: horizontally on Top or bottom w/hoses upward, or vertically in front or the rear w/hoses orientated on top or...