I would guess much smaller on idle and main jets. They do make idle jets as small as .40, .45, .47.
1.80 or 2.00 air jets usually make it run OK.
Smaller motors like F7 emulsion tubes sometimes instead of F11.
Main is usually 115 for a 1915. I'd ask @Lane Anderson what jets he was running.
Do some searching on aircooled.net, they have good reading on jet sizing.