What clutch? Chances are good that clutch is getting too hot. How does it shift on the return lane? Normal or notchy?
If it shifts fine on the return lane then it just sounds like a foot-hand timing issue, and that just takes practice.
'04 Mach 1. Built. Turbo. 667whp/631wtq
'06 Focus. Built. Turbo. WMI. (sold)
'03 Mach 1 : 12.61 @ 106.59 (sold)