The XL is quite a recent thing, last 3-4 years maybe?
One thing you could consider, it's drastic but I have done it, is to use a 140mm travel aluminium lefty max, and then use a 20 or 40mm travel bumper inside to limit the stroke to 120 or 120mm, then remove **half** the key-spike in the lower crown, this allows you to drop the lower crown by about another 20mm, thereby extending the available space between crowns by 20mm.
I used the above method to fit a slightly long headtubed intense frame. It still wouldn't allow you to fit a normal lefty to you banger but if you can adap the same method to an XL it might help.
What I'm not sure of is if the XL is available on forks with removable crowns as a lot of the more recent leftys have the crowns bonded to the leg.
Have you looked at project 321 converters? they may do a top drown with extra drop to allow fitting to longer headtubes...
One thing you could consider, it's drastic but I have done it, is to use a 140mm travel aluminium lefty max, and then use a 20 or 40mm travel bumper inside to limit the stroke to 120 or 120mm, then remove **half** the key-spike in the lower crown, this allows you to drop the lower crown by about another 20mm, thereby extending the available space between crowns by 20mm.
I used the above method to fit a slightly long headtubed intense frame. It still wouldn't allow you to fit a normal lefty to you banger but if you can adap the same method to an XL it might help.
What I'm not sure of is if the XL is available on forks with removable crowns as a lot of the more recent leftys have the crowns bonded to the leg.
Have you looked at project 321 converters? they may do a top drown with extra drop to allow fitting to longer headtubes...