just a twisted suggestion....
Inspect the the 8mm dia vertical mount bolts for zinc oxide build up (white), if noticeable lightly wire wheel the threads (they tend to bind) and coat lightly with anti-seize compound (be cautious of your choice). optional torque spec for this application ..... when in doubt: assuming you are threading into aluminum without inserts as opposed to steel, the 20 ft. lbs. nominal was not too are off (allowances for lubricant type ignored for the moment), you "can usually" feel (provided you are not binding) when they start to striiiippppp!
On the 10mm dia.'s if you are going into steel you can go up to 30 ft lbs.
When all else fails, scream "who stole my Machinery's Handbook, 27th Edition" ?
Available at a great price here:
http://www.amazon.com/gp/product/0831127007/ref=pd_sl_aw_alx-jeb-9-1_book_5406959_14/104-0711734-5665537?n=283155
Lots of resources on the net:
http://www.engineersedge.com/fastener_thread_menu.shtml