So, yeah, the Estoril is a big pipe.
Needed to rush to make pedals work. Came up with a cheap and super accessible solution I haven't seen before.
The clearances for this are going to be based on making a '78 Swinger 1 work with a side bleed Estoril. I think that means it'll work for most Maxi's and maybe the Magnums as well.
Will be open here; not sure of the longevity yet. There is a small amount of movement after 2 hard days of ripping around a kart track. Might just be loose or squished grub screws. Will update.
I got all my parts from my local Ace Hardware for about $10.
2, 5/8" ID shaft collars, 1/2" thick and mine have a ~1" OD.
2, 1/2" 1/4-20 grub/set screws or whatever appropriate thread fastener fits the collars you find (grade 8 or 10 if you have the option; the shaft collars are also usually hardened)
I ended up welding the collars together 90 degrees rotated for better mechanical holding. 180 off might be best.
Doing it over, I would drill the holes in the pedal shaft twice as deep as I show here and get appropriately long screws. Drilling deep and tapping the hole would be extra fancy.
And while I know it looks close, I didn't have any issue at all with the crank hitting the pipe. (edited)