I worry that you won’t have enough room for the Sniper to fit under the hood with your current design, IF you’re planning on using it in a GT. If not, then I have no clue of the available room in another model of Opel.
I have the Manta B mounts on my Euro 2.4 setup. Using my Cannon intake, along with my intake snorkel on a Sniper 2300, I am barely fitting under the GT hood. The pitch on this prototype intake is too extreme for the GT. If you could merely level the Sniper against the angle of the motor in a GT, you would have a good starting point. If you could drop the initial mounting height for the Sniper, to allow for a spacer, that would be miles ahead of what is currently available.
Don’t forget, if you have a high-port head then your intake is already 5/8” higher than the 1.9 head’s.
For me hood modifications are outside the scope of this project. One of the design criteria is definitely "fits under hood of a GT"Here's another thought...Manage the mount height for the Sniper, and the slope the floor of the intake plenum, to facilitate a downhill flow. Doesn't seem like it would take much slope, but anything flowing below level would be an improvement. Beyond that, you are looking at needed hood mods.
One of the cool things about this design execution is that I built the CAD model based on parametric design. So, the parameters can be tuned and the model adjusts itself. In the original version the plenum is at a 30 degree angle. But if we need more clearance for example, it can be adjusted. I went in the model today and punched in 45 degree angle on the plenum. This parameter along with a few others allows for making it taller or shorter, narrower (to preserve the heater box), etc. It is not quite that simple, but that is the principle. The original execution uses 3 inch center line radius curved 38 mm diameter tubes for the inner ports and a 5 inch center line radius for the outer ports. I was aiming for standard mandrel pipe bender die dimensions, as I had initially planned on making or purchasing mandrel bent 1.75" tube with 1/8" wall, that would give us the 1.5" (38 mm) inner tube diameter. Now, however, I am planning to just use cast the arms out of aluminum. So, I can move away from standard tube radius measurements (one more degree of freedom helps free up the design constraints)! So, all I had to do is redraw the 3D rail that the runner pipe loft follows and voila! Below is the quick rendering / sketch concept from CAD at an angle of 45 degrees . It does not require any changes to the plenum, just printing and cast new arms molds and sand core molds.
I just finished machining the ports in the head flange on my mini-mill today and drilling the holes for the alignment pins. So, I should be able to test the fit-up in my Opel GT this week. I must say that this hand machining is a lot of work! I can see why Rally Bob used to get these waterjet cut. Batch cutting is the way to go if you need to make a bunch of these. That said, the piece of aluminum only cost $15, and my labor is free. So, I will just chalk it up to therapy (although, not as therapeutic as casting hot molten aluminum).