The radials on these antennas truly do not much more than to help with CMC issues. And the A99 is a okay antenna, but they need height to work work a hoot. JMO. Truly have a look at the Sirio vector 4000. It is one of the best vertical antennas made for 11 meters. Do some reseated on the A99 and the IMAX 2K. If anything the I2K would be a better choice out the of the A99 or IMAX 2000. But again, the Sirio vector 4000 will beat both of them out as far as rx/tx capabilities. The only issue with them is how long they are, they will sway a bit in the wind depending on how you setup the antenna. Mine is next to my chimney and is bolted to the house, and the top the of the chimney. I also have added some black paracord and it is virtually invisible from any distance other then right on top of it. My antenna is at 26ft to the base and the tip is at approx 52ft. The antenna is 27.82ft long. It's a 3/4 wave antenna. And I swear it blows away the A99. Lower floor noise and much more distance both TX and RX when the bases are at the same height. It doesn't stick out too bad if you have a few trees. It is not as bad as an IMAX 2000 with a GPK kit would look. Again, JMHO.
I ran an A99 at about 28ft to the base of the antenna and it worked mediocre to say the least, for me anyway. I wouldn't take one if someone gave one to me now!!
But this is JMO, and my own experience with the A99. The IMAX 2000 is a different story as its a lot longer. Which makes a difference. Same with the vector 4000. It's right at 28ft long. My tip height is 54ft. You'd need to place an A99 to over 30ft to the base, actually 36ft to be exact to be at the same height as I am with my antenna. Height equals might. Not saying the A99 won't work. They do. But they also splinter and after a few years are done as most of the time water gets into them or the cap in the bottom for impedance matching takes a crap. Depends on where you are located I suppose. The FL sun does a number on them. Mine was sanded and painted black and still splintered. I ended up giving it away after using some HD heat shrink on the entire antenna to not get splinters in my hand.
Sorry I am just not a big fan of fiberglass. Here is a couple of photos of my Sirio vector 4000. It's located in my backyard. No one has said a word about it and I live I an HOA and I have not had any issue with anyone saying a word about the antenna. Truly I haven't. I did get some complaints about the A99 causing some RFI/TVI issues with my next door neighbors. Since changing antennas no issues at all. Maybe it's just me. But anyways. Sorry for the text wall. Hope this helps at least. If you do go with the A99 or the IMAX 2000 do get the GPK kits. They do help with CMC issues. And also add a low pass filter after your radio. Bencher makes a good one and also RF limited makes a decent one for the money. The DF3000 or DF4000. Something like that. Again, have a good one.