I love shooting my X5 Legion.  The weight of the frame really does improve controllability.
The one negative is putting it back together after cleaning!
The recoil spring is very long.  Trying to get the spring and guide rod re-installed and seated in the slide is a frustrating, time-consuming process.
The long spring likes to bow out instead of seating.  Passing the guide rod down the spring often gets blocked and gets caught on the front end of the spring.  I've tried placing a plastic cleaning rod down the front of the slide and down the spring to help the guide rod pass, but it turns into a three-handed cluster.
Anybody else been through this?  How have you solved this challenge?
I don't want to launch my recoil spring and guide rod across my reloading room any more!

This is what I do.
I get as much compressed as I can and pinched between my thumb and middle+ring fingers(right hand) while holding my index finger on the base of the guide rod. You have to hold it very tightly. Then I hold the slide in my left hand with the top to the left and the underside toward my right hand. I put the end of the spring in place and get the guide rod started down the hole while reaching around the slide with the fingers of my left hand and sortof pulling the spring/guide rod toward the slide while pushing it down the hole. Then I slide my index finger off the base as I set it on the barrel lug.

That was way more to type than I anticipated

You can also try putting the slide upside down on the floor and pinching the front and rear of it between your shoes. Then using both hands to compress/hold the spring while guiding it in the hole and seating it in place.

Pre-compressing the spring as others have mentioned is the best I’ve come up with.
Honesty, I find it to be such a pain in the ass that I’d buy a captive guide rod spring for mine if I could. (I’m assuming they don’t exist. Maybe I should look)