Can you "safely" use hcg in the middle of your cycle to "spark" your nuts a bit? 
every how many days and duration?
The benefits of using hcg throughout a cycle have been debated here and on other sites
ad nauseum. Those who have read my past posts on this know that I favor low dose hcg throughout the cycle, and there is more than enough scientific evidence to support this.
That said, I see no reason that you can not introduce hcg in the middle of the cycle. Depending on your cycle composition, a relatively low dose of 300-500 iu every 5 days should suffice.
I continue that regimen throughout my cycle, and during PCT. I don't subscribe to the large doses at the end of a cycle. It's a matter of "preservation" versus "salvage" of Leydig and Sertoli cell function.
Which sounds better to you?