Modification of your gun. (It's not a major problem though)
I bought the enite air-through kit from the manufacturer's site last month, and I can already see that it was well worth the money. The stock is as sturdy as a regualr rifle stock, and much more comfortable. It fits quite snugly into the back off your A-5, and it may take a few minutes to jam the pins back in. After that, it won't wobble a bit.
The air-through design is also very nice, since the remote line attaches to the bottom end of the stock so that it's not in your way. The foregrip is also quite nice, though my opinion may be biased since I am more inclined to using horizontal foregrips. The foregrip is, however, optional for those who are more at home with vertical ones.
Great stock, the best I've ever seen or used. it's definately worth the $120 you pay for the entire kit.
If you choose to go with the air-through design, then let me warn you that it does require some modification to your reciever. It isn't particularly difficult, just make sure that you or whoever is going to modify it know what they're doing. You don't want to end up with a uselss left reciever.