patmat2350@ELCOPT Rest assured, the vast majority of the cost goes to Shapeways, and not to me, the designer, for these parts WHICH ARE CUSTOM PRODUCED TO ORDER USING ADVANCED PROTOTYPING PROCESS. I make my designs available to others to help them out, since no one else offers them through more affordable processes that involve hard tooling.
Regarding size: I can assure you that the parts are correct to the stated scale; did you order the correct scale? Perhaps you ordered 1:24 parts instead of 1:20? The scale must be selected at time of order. If you did order 1:20, please let me know what appears to be too small.
No, the tube is not much bigger, it is thin wall steel... about 1/4" [6.3mm].
Your reference is a secondary source... I have the original Elco torpedo tube drawings. The actual inside diameter of the breech collar is machined to 21.41 inch... 27.2mm in 1:20 scale... actually slightly smaller than the (approximate) tube outside diameter I mentioned below.
Regardless, these parts are sized to fit 3/4" PVC pipe, which is commonly used by modelers for 1:20 scale PT boats.
The actual tube outside diameter was 21.75 inch; /20 = 1.088 in = 27.6mm.
3/4 inch PVC pipe is used in the Dumas 1:20 kit; it has an OD (outside diameter) of 1.055" = 26.8mm.
For R/C use, I highly recommend using thinner material, as the PVC pipe is quite heavy. I used a lathe to bore out the PVC pipe, and removed about 1 kg. with four tubes.
Sorry, I don't have the design tools to do "soft" items... look up my buddy Holden8702.
Pedestal- this one is 1-5/16" tall in 1:24... and very close to 1-1/16" diameter (not counting the foot rests). It looks right to me, while another 9/16" height would seem like too much.
Until I get to touch and measure a real one in person, I'll remain dubious of all drawings.