Increasing your dosage of testosterone from 250mg/week to 400mg/week for the last 5 weeks of your cycle is kind of pointless if you are using a long estered testosterone like test e or test cyp because the hormone won't reach peak blood hormone levels until 3-4 weeks after the increase of dosage.
If you are using a short estered testosterone like test prop, you can increase your dosage from 250mg/week to 400mg/week if you want. It's up to you. I don't suspect you will notice a huge increase from the additional 150mg/week.
Rather then increase your testosterone dosage, I would add in cardarine to your cycle. Cardarine is a great addition to any cycle that contains tren. It will directly increase fat loss, endurance and help to reduce tren related side effects.
http://www.evolutionary.org/cardarine/