Mark...
I got 2 100 mm pole holders in my 2011 swan..got them from the jayco dealer when i picked it up (installed at no charge) and they were fully aware that the 150 mm wouldnt fit under the front boot...
Will try and get a photo of the setup, but basically the are held on by brackets around the drawbar.. The end caps are push on, with a large pin and split-pin holding them on...
Note that with bed flies and an annexe, it is a tight fit though, but it all fits, including poles, ropes and pegs..
Rob