In Tajweed science, there's something known as Al-Tahqeeq (Slow), Al-Tadweer (Medium), Al-Hadr (Fast). And the best one (for me) is Tahqeeq, because it gives you time to think about the Glorious Qur'an.
Sometimes when I'm reciting Al-Fatiha behind the Imam, by default I recite at Tadweer, but sometimes when I'm at the 6th or 5th verse, he goes down for ruku'. So I start to recite very quickly (Hadr) so I don't miss the recitation of Al-Fatiha.
Is it permissible to switch between the speeds of Tajweed this way while reciting?