[Tony Wheeler]

Hi again Tony,
It has just occurred to me that this pic demonstrates clearly why you'll need a fatter rear crossmember. Imagine sliding this F15 rear crossmember forward inside the chassis rails, to a point underneath the tyre somewhere. As you can see it would be very sloppy inside the chassis rail channel, because it's much wider there, due to the taper.

This is exactly what you are doing by shortening your F60L chassis by a massive 43". Remember that the rearmost 7 foot or so of a blitz chassis is identical on all models, so in looking at this pic, you are looking at an F60L chassis.

I realize it's difficult for you to visualize on your chassis, because the rear section is no longer there. Hopefully this pic helps.

Cheers