CCE to FB to Holy Grail - Installing insert in EVA foam/Precision putt turf area

[Gstmike]

So after using the CCE mat initially in my sim room and finding it a bit too punishing even for occasional use (digger), I went to the Fiberbuilt studio mat which has been used outside with my Net Return while the weather has been good. But now with the season change sim golf goes back inside. And I wanted to improve on the grass hitting area of the fiberbuilt studio mat for indoors because it can still feels i'm hitting off a broom.

I decided to try the turf/hitting insert thing and just recently put down the Synlawn Precision Putt turf over 1" thick EVA foam tiles to cover my entire indoor sim area (14'W x 15'D).
As some have mentioned, the EVA foam/turf combo can be a bit "squishy" but likely not a problem for stance, putting, or anything golf related. It IS a bit annoying to move things around on though. Anything with any weight starts to embed into the turf/foam after sitting in the same spot for a while (like my computer/monitor cart which is on casters) so a bit annoying to move things around on.

My next step will be to cut an opening and install my hitting insert. Still waiting to take delivery of my 12" x 30" hitting insert (Holy Grail from Gungho Golf) but a bit weary of cutting a big hole in my expensive putting turf so I want to make sure I get it right the first time.
So if anyone can provide some advice or input on any of the info above, please do. Should the opening be exactly 12" x 30" or does the opening need to be cut bigger or smaller to get the right fit/performance? I've posed the same questions to Gungho golf but figured I would leverage the forum expertise as well.

Thanks all.

[ExplorNH]

They include the dimensions you need to cut on the instructions in the box. I outlined the holy grail on the backside of my mat and then cut and it came out nice. Just needed a straight edge, sharpie, and razor blade and about 30 mins of time.

[mp1972]

From their website: "we recommend cutting the hole to 12.25x30" to have a tight fit front and back, and a 1/8" gap on each long side to allow the strip to cleanly deflect downwards on strike."

I haven't received my turf yet, but understand the weariness comment...already scared to do this step.

[barwick11]

I just got my holy grail in the mail yesterday. It's lovely. I was playing on a cheap mat and my body was getting beat... up...

Today just played two full sessions and it's a night and day difference. Super easy on your body, that much I can say. Fat shots are still punishing, but not nearly as much as they were with the cheap mat (I'd snap hook an iron 60 yards left if it contacted the cheap mat before contacting the ball). It still yoinks the ball left with the holy grail mat, but not nearly as much.