Synergistic HFT’s with Martin Logan’s

Is anyone using synergistic HFT/FEQ with Martin Logan’s, or any other panel or electrostatic-speakers? Any placement notes??? I was thinking I could expand my sweet spot... I started with 12 HFT and ended up creating this space that sounds huge... notes just hang in the air forever. The speakers are still there, but I haven’t received my FEQ yet, and I haven’t done the speaker HFT speaker kits. 
What are your thoughts ?