The extended X chocks won't work either. I have a White Hawk 27DSRL. I measured the "tread to tread" distance between the axles and it's greater than any manufactured scissor chock would effectively span, but the distance figure escapes me at the moment (CRS Syndrome). I have seen some nice homemade chocks made for wide set axle trailers on RV.NET, but I just went with 4 of the Valterra plastic wedge chocks and they do fine.
If you plan to do any suspension enhancement, such as adding the Dexter EZ-FLEX, you will be similarly disappointed. I asked our selling dealer about adding it to our rig prior to delivery, they couldn't find a compatible kit in Dexter's catalog. A call to Dexter's engineering department revealed Dexter doesn't have an EZ-FLEX product that will work with wide set axles........and Dexter makes the running gear the White Hawk rides on (BTW, the center to center measurement on the axles is 42").