Questions about making a 3/8-in doweling jig

[nomon]

Since the 3/8-in doweling jig is NLA, I thought I'd make my own. If you don't mind, would you answer a few questions for me?

What thickness of acrylic is best? 1/4-in ? (which seems to actually be 6-mm = 0.236-in from most sources). The prices I am seeing for a square foot of acrylic are almost the same for 1/4-in or 3/8-in thick (just under $20). Would 3/8-in thick be better than 1/4-in thick?

Can you provide any advice about spacing of 1/2-in holes in the acrylic? What is the minimum safe spacing do you think? I was thinking about putting two rows (offset) of five 1/2-in holes with 5/8-in center-to-center spacing, but that only leaves 1/8-in of acrylic between the closest parts of the holes, so I was thinking maybe I should go with 3/4-in spacing.

Where is the best place to get the bushings these days? Are you still using "spacers" aka long washers? I looked around for precision bushings and I found that McMaster-Carr has 3/8 x 1/2 x 1-in drill bushings (part number 8491A727) with 0.001-in tolerance on the diameters, but they cost almost $12 each (plus shipping). Lowe's has 3/8 x 1/2 x 1.5-in spacers for $1.39 so I am wondering if they are good enough.