Here is a photo (posted at the end of my post), of a truck that did a Sirio trucker 5000 with a 36" bottom shaft he had made or bought from someone that makes antennas like Predator Antennas , Monkey Made Antennas, Mr. Coily Antennas and so on. Let me see if I can find the longer 36" shaft. He did mount his to the mirror and not the factory mount on the upper portion of the left side of the body. Above the sleeper area. Not sure if your truck is set up like this or not. But since you were placing longer shafts together I figured these photos might help as far as whip length and also bottom shaft, both where to buy a long one and also how it looks mounted as well as the whip length. Here are the pics. Notice how short the top whip is compared to a stock one. He used approx. approx overall length of 7ft. So that would be a 36" or 3ft. bottom shaft, and not including the coil which on my regular Sirio 5000 is approx. 6" or so that the top whip is about 3.5ft give or take. It depends on where you want to tune it for resonance. If you want it cut for 27.205, start with the whip at about 42" for the top whip and this is with using a 36" bottom shaft. For your 2 shafts placed together, you would need the whip to be approx. the same length as what I posted. Basically with the whips you used, if you would have used the 48" whip and cut it down to about 42" then fine tune it from there, you could have gotten the VSWR down. But the way you had it both whips were either too short or too long and this is what most likely resulted in the SWR readings you saw of 2.5:1. I would think that with a proper length whip that you could get the VSWR almost flat or flat if you really take your time. I cut in 1/8" increments, but for a starting cut I will cut 1/4" and then step it down to roughly 1/8" cuts. Yes it takes longer, but I retain my whip length being all the what down in the hole also don't cut it too short as well. If you don't feel like messing with the firestick I understand, but I will say that a 7ft antenna should perform better then a 5ft one. With 2ft. more antenna it should make a difference in overall transmit and received signals. JMHO. But like I said, you have cut your whip accordingly to get it to be the correct length. You want it to be approx the same length as it is stock. Which is about 7ft total length. I hope this clears some things up and hope the pics help a little. Have a good one.