Stretching but not mobility

I'm currently on an intense weight training program that runs for another 9 weeks. I wish to complete this.
Fundamentals has taught me I'm extremely tight everywhere, especially lower posterior chain (go figure.) My Stiff Bear is a joke. 
I want to start foundation 1 and handstand. If I wait until I finish the afore mentioned, I'm looking at 8th Aug.
I have all 3 stretch courses and have started do them.

My thoughts are thus:

1- Do as I am now, weights/stretching and repeat various relevant fundamentals, wait 'til Aug and hit F1/HS.
2 - Start F1/HS now alongside '1' but potentially overtrain.

I know I'm tight and I feel like the stretches are a really helping, but I'm concerned that I'll lose out on 9 weeks of mobility and the associated adaptions that will take place. That's 63 days out of my ~200 that are potentially wasted. Then again I don't want to over train because that'll be worse.

So having taken the long way around, my question really is this:
How much mobility work will I get from the stretches and fundamental exercises against what I would get from F1/HS and am I likely to 'miss out' on connective tissue adaption and growth if I don't start mobility right now?

I would go with plan #1, provided it includes the stretch series. I would never mix and combine different strength programs. You say what you're doing is intense and you're stiff. Hence mobility is/should be your priority. You're not going to miss out by starting with the stretch series. You're going to gain mobility, gradually.

To your last question, it's pointless to compare different GB courses that have complementary functions. They're all meant to work together.

You already stated you want to finish the strength program you're currently doing. Ok. Do that and then get on the wagon of F1/HS. Aug 8th is around the corner in training years anyway.

On a personal note, when I discovered GB, I couldn't wait to get started. I don't like wasting time, energy or resources either. If I find a better way, I've have no problem quitting something and changing my plans.