The first batch of stacks I ordered had some slight dimensional mismatching as a result of material shrinkage while it was printed. I've adjusted to compensate for that, slightly undersizing the joint between the printed part and the throttle body. If the next order is off, its going to be off in the direction of being slightly too small a diameter so I can sand it out to sit perfectly flush and leave no lip at all. After thinking it over and handling the material some more, I'm not confident in a printed backplate without making it 4-5mm thick, which becomes extremely expensive.
I've found a proper sized rubber coupler to avoid the **** fight that is slipping 60mm reinforced silicone hose over a 62.3mm connection. Its cheap as chips, and you can cut the 3" piece into 3x1" connectors for my design, which has a reinforced 1/2" mounting are for the coupler, and the other 1/2" will sit nicely on the TB.
Below is what will probably be my final solution. Holes are 4mm for mounting, intended to be used with these two items, 4 of each:
Aluminium Dome Head Bolt M4 x (0.7mm) x 12mm Extra Large Head
Aluminium Nylock Nut M4 + loctite to ensure nothing works loose
The holes for the stacks can be drilled with a 2.5" hole saw into the backplate, as the mounting flange is larger than 2.5" and will require only a small bead of silicone around the base up against the stack to get squished while assembling to create an airtight seal. Still working out how to seal the filter to the backplate after the whole assembly is mounted to the throttle bodies without using the standard pipercross mounting tabs (may end up having to do so.
Final design, its the best balance of price/simplicity I could come up with. The base has a 1mm ring 1/2 way up the mounting area to give the clamp some edges to bite against. Standoff from the TB to the backplate is 50mm, total stack height, 75mm. The protrusion into the filtered area will help prevent water from running in while the bike is sitting in the rain, overall width is 317mm, internal width of the PX-500 SHOULD (pending measurement next week when it arrives) be 320mm:
Shapeways Printing Cost: $109
In the pink render you can see how thick the bottom 13mm are, its to allow a perfect match to the TB outer diameter and simplify installation. The nylon allows quite a bit of pressure from a hose clamp before deforming so it should be able to hold on quite well with this method.
