Racket:
I've been following Kova for a while now, and I'd say he's probably using the Wilson Blade 98 16x19 (count the strings in the picture below) v6 Countervail version (probably L3) as that's what he used in college at Illinois and when he first came on tour and we know pros rarely switch and just get paint jobs after their tour debut.
College Specs:
Tennis Warehouse has a stock strung Wilson Blade 98 16x19 v6 Countervail listed at...
11.3oz/320g
13.1in/33cm (3ptsHL) balance
326 swingweight
We see in the pictures below that he's added approximately 10-12 inches of lead tape from the 7th to the 17th cross from the bottom for a total of 20-24 inches or 5-6g and increasing the swingweight by approximately 12 points and lowering the balance by 1 point. We also see what looks to be approximately 6g of lead in the throat which won't affect the balance and bumps the swingweight up ever so slightly and of course we will add 6g and 1ptHL for his overgrip.
With the visible customizations we can speculate his college frame comes out to...
11.9oz/338g
338-342 swingweight
13.1/33cm (3ptsHL)
Now Blades come with a foam filled handle and we have no way of knowing that he didn't dig it out and counter weight his frame. However, I will say that some of the pictures of his grip below from when he was in college look a bit chunky as if he has two overgrips to compensate for the low headlight balance. It's also possible that he's also using a leather grip and two overgrips to increase the headlight balance as well as dampen the potentially harsh feedback and feel of the leather grip.
If he was using two overgrips and a stock synthetic grip his college specs would come out to...
12.1oz/344g
338-342 swingweight
4-5ptsHL (approx.)
Pro Tour Specs:
We see in the newer more current pictures below that he's cleaned up his frame since college and has no exposed lead anymore. I often see college players with a lot of lead at 3 and 9 and none at 12 and then go the other way when they hit the tour. I think this is a common trend when players are transitioning from college to the ATP as the tour and modern game requires more power, spin, and plays much faster overall and a lower static weight and less sluggish frame is more beneficial.
Now theorizing he's still using the same v6 Wilson Blade 98 16x19 Countervail with no exposed lead he would need to have approximately 4-5g of lead under the bumper at 12 to bring his swing weight into that 340-342 range. His grip in the more current pictures below looks less chunky and the bevels look sharper from when he was in college so I would theorize that he either...
1. He's using a leather grip and overgrip to counter balance the lead at 12.
2. He dug out the lead and counter balanced the lead with silicone.
3. He kept the foam in the handle and is playing the blade stock other than the lead under the bumper (highly unlikely).
And of course taking his 6g overgrip into account I would theorize his current specs to be around...
12oz/340g
5.5ptsHL (approx.)
340-342 swingweight
String and Tension:
This one I can confirm as I spoke with Curt from Custom Tennis Rackets (he's a super nice guy and does a great job doing custom paint jobs, he did one for me last year) who strings for Kova. He told me that Kova strings with Luxilon ALU Rough at various tensions but usually 46lbs most of the time. This makes perfect sense since ALU Rough is known for being a very connected and crisp string that paired with a Countervail Blade (well known for it's lack of feel) complements it will. He was unsure of the specs as he told me that Kova's customizations are done by Wilson.
