I m going to run an external turbonetics gate (cause I have some) to bypass the small turbo. My plan was / is to just not overspeed or beat up on the stock turbo to much. I have no idea how it will work, but I think wasting at around 20 psi on the stock turbo should be pretty good, I just hope the 3b is producing by then, hopefully by 2000- 2200 rpm. That way pulling a hill in 4th(3.54's and 265 tires) at 2300 to 3000 the egt will stay low and hold boost overall to 50 with a second gate if needed. I hope it works, especially with a heavy trailer, like 15k-20 k area.

 

Why not use the stock wastegate on your HX-35 turbo? I have the PDR 3b/40 set-up and that’s what they use. The PDR40 wastegate is set to 40 psi and I'm sure that your HX-35 will live with the gate set at 30 psi. My 3b doesn't have a wastegate. There alot of weight hanging on that exhaust manifold. Most people up grade to an ATS exhaust manifold and have a support bracket to support the 3b from under. You may have to drill a bung into the oil pan for the return on the second turbo. My set-up uses two adjustable pressure relieve valves on the tube going into the intercooler. Another trick piece of the PDR set-up is the custom down tube off the HX-40 into 3b turbo. You remove the plate off the bottom of the wastegate and bolt up the down tube. This reduces your drive pressure and allows you to use your wastegate pressure more efficiently to drive the 3b turbo. Also re-torque your head bolts, just to make sure that there snug. Down the road your probably going to have to o-ring the head and install studs.

 

With the stock wastegate won't the backpressure be to great, that's alot of air trying to go threw a little hole. I thought maybe boost the small turbo way up and then ease it back as the big one takes over. It seems a 35-40 don't mind 43 lb. of boost alot, then let it back down to whatever it takes to make around 50 with both of them.I'm just looking for a tow setup with control of exhaust temps without letting out of it as much.

 

I'm not an expert on turbo wastegates but this is how my PDR twins are set-up.
My thoughts are that a internal waste gate will help develop more drive pressure than an external waste gate as the waste air is re-directed back into the primary turbo. This will help to increase the primary turbo's boost and allow to develop more overall useable boost. The stock waste gate are large enough to protect the turbo in most cases. You just have to bleed off some of the air to protect the secondary turbo. Assuming that pressure on the waste gate has been set correctly. This will help to prevent damaging the secondary turbo and as well helps to build decent cool boost.