Strong first post.First of all, this routine has a poor set up. Every muscle group in the body as GymRat reminds us should not be isolated. Isolations are intended to assist compounds in bringing up lagging parts, if EVERY muscle group in your body is lagging you have a deficiency in nutrition and/or your training principles all together.
6-12 reps isn't for hypertrophy. Weight is more important. I can do 6-12 reps with the bar all day long and not respond unless I apply weight. The way to reach the point of high weight in your compound exercises is by applying to progressive resistance using 4-6 repetitions. Once that base of strength is generated and you're capable of bench pressing 1.5 your bodyweight and/or deadlifting double your bodyweight then it's a reminder of being time to begin using the 6-12 reptition rule (if necessary).
When using 4-6 reps, your hypertrophy gains will plateau before your strength gains, when using 6-12 reps your strength gains will plateau before your hypertrophy gains; however, it is at this extent difficult to get any bigger unless you're adding weight.
If reps were more important to getting big than weight bodybuilders would have no reason at all to apply more resistance to the bar, yet they always do BECAUSE weight, stimulus AND reps apply to muscle building.
You pretend it's hard to get big, when it's not. Routine isn't the answer to gaining size as much as the nutrition in which you have posted very little content about. An ectomorphy has a deficieny in the ability to gain weight which should brilliantly portrary that it's the NUTRITION he needs educated in not an unnecessary split with useless rep ranges and exercises that aren't relevant to his goal. He is to decide which bodyparts need isolation, NOT you. You don't know him as well as he does, with that if he's a beginner he should just stick to compounds and once again apply to progressive resistance until he is ready to listen to his body and apply his own isolations.
Four factors dictate size.
1: make sure you're eating enough good quality food in order for your body to grow.
2: Make sure you're lifting weight with enough intensity to micro damage the muscle, Could be anywhere between 2-8 sets and between 15-40 total reps. Example: 3x5=15 or 4x10=40 The choices are endless...
3: Make sure you're progressing workout to workout. either more weight, more reps faster tempo, etc.. make sure your workout is more challenging than the previous one.
4: make sure your routine primarily consists of compound exercises such as squats, deads, cleans and presses. Isolations should be 0-10% max of your total exercises.
that's it... Implement those 4 things into your workout and you'll gain both size and strength.