Unfortunately, the information in the Define 7 XL manual is incorrect.
It lists that there is a 36mm max motherboard component height for top mounted radiators, but this is only if you are using an EE-ATX motherboard.
If you are using these following motherboard form factors (E-ATX, ATX, mATX, MiniITX, SSI-CEB, SSI-EEB)
There is an 80mm clearance from the top fan mount to the top the motherboard form factors listed above.
If you are using either a radiator that is using 140mm fans, or if you are using the 120mm fan rails closest to the motherboard you would have a maximum total thickness of approximately 95mm before you would reach any motherboard component restrictions.