If he has too much of a 19nor in his system (more than or equal to the amount of test mg vs. mg) there is a very strong possibility of having libido issues that only cialis can correct, and then at that point if he can maintain an erection he won't be able to finish.
The TOTAL mg of both compounds should be less than the 500mg of test weekly, and might even have to be lower? Everyone is different.
If it were me I would drop the deca 10 days before starting the tren. Then I would use the tren at 50mg ED NOT EOD. Having ED injections keeps blood levels stable and reduces sides to almost none, in my limited tren experience. Use the slin pin method for this as it will reduce scar tissue with ED injections.