Everyone knows that 3-foot antennas for CB band severely restrict RF performance and efficiency and provide a very narrow bandwidth, but it's something us city dwellers have to settle for... I've owned Wilson Little Wil and Sirio Turbo 800, both of which are 3-foot tall and work surprisingly well! Without an antenna tuner, both antennas achieved flat SWR mid-band and 2:1 at the edges. With an antenna tuner (MFJ-945E) I was able to get them down to 1.2:1 at the edges. This is barefoot, using Uniden 980 SSB and CRE 8900.
I then started experimenting with more power (dumped to dummy load, of course!) to see how both antennas reacted and to see if they were really able to handle what the manufacturer claimed. This is just my experience, others might have different results. Both antennas handled 100W dead-key like a champ with 1.5:1 mid-band and 3:1 SWR at the edges. The antenna tuner brought these values down to 1.2:1 mid-band and 1:5:1 at the edges.
At 150W Wilson reached it's limit and would not tune but Sirio still performed great with no SWR increase. At 200W Sirio started to experience SWR anomalies, during dead-key the SWR would start out low but immediately start creeping up. At 200W same thing, but it would rise faster. I didn't try any higher and called it a day. Since the amp was able to produce 300W I started searching for another 3-foot antenna that could handle the load... The answer was Midland LUX700 which is rated for 600W @ 50% TX 50% RX duty cycle.
I ordered it from a company called Avera for $60 and it shipped from Europe via FedEx International. I was surprised when it arrived in mere 3 days, to the Midwest USA! It's just a few inches taller than the Sirio and is heavier, maybe due to larger gauge coil. The whip seems to be the same diameter. I was able to tune it to 1:1 SWR mid-band without much difficulty. With and without the antenna tuner it had the same SWR performance as Wilson and Sirio, barefoot, and with 100W.
The moment of truth, at 200W no change in SWR and the needle is not creeping up. Same at 250W and at 300W, so I think we have a new winner! So far I'm very impressed with this antenna, low profile and handles 300W like a champ. As a bonus, when you key up the base of the antenna lights up which is kinda cool.
Anyway, this is my experience, your results may vary.