Can you mix German Volume Training and Stronglifts 5x5 ?

My personal take on it

Based on 10 month on 5x5 & one month of GVT

• No, if focus is muscle gains
  
  • I found GVT to be the best program I have been for muscle gain with 5kg in month while losing strength. Therefore focus on GVT only
• Yes, if you have the time
  
  • By all mean if you have the time to do a session of 10x10 and 5x5 on the same day, be my guest. Maybe cyle the routines in a way that you do upper 5x5 / lower 10x10 on one day and 10x10 Upper / 5x5 lower on other days. Otherwise you will put yourself through even more unnecessary pain if you do 5x5 and 10x10 upper.