It's perfectly okay to use a turret head attachment with a counter-balance truck if you comply with the manufacturers lift ratings(attachment and truck). The attachment manufacturers should be able to help you with guideline figures but these are purely guidelines. On a 3 ton counter balance you should be able to work about 750Kg on a turret head safely..but don't take my word for it as the truck type and tyre type etc. all need to be taken into account.