ATC SCM19 V2 Recommendations.

I opted for just over shoulder toe in that gave me best sound stage.Directly was good but i  felt that over shoulder gave me broader stage.Your stands look worthy enough.Big believer in sound anchors for atc's.If they are spiked make sure they are secured to floor!...all i know is the effort really made the difference with the 19v2's.They give back whats put into it.Like the power rating from amp!

Brad (lm) knows these things...🎶

I'd fill the stands with dry play sand.  It will provide a less resonant foundation, and less easy to tip.

@kb54 

The stands are filled with something heavy already. Each one weighs about 25lb.

@tony1954 

Whatever sound the stands make, that is added to the speaker.  Mass is your friend in stands so the fact they are filled an don't resonate is good.  42" away sounds good.  Now how far from side walls?

So you are a Brit too!  Well if you ever go back, call them a week or two ahead and get an ATC factory tour.  It's fascinating because it's the way all the speaker makers used to look (winding coils, building drivers, etc ) but almost none look like that now.    Most buy all the parts/cabinets from a third party.  

+1 on the Sound Anchor recommendation, I used them for JBL and Westlake monitors. I still have a 3 leg pair for some vintage JBL’s. What is nice is that you can attain an exact height, and exact footprint for your speaker cabinet. Warning , do not use the blue dots as they will decay and release oils/chemicals into your speaker cabinets. Also their black finish ,while attractive is subject to wear from handling as they mix a course substance into the finish. Cheers , Mike.