On a standard 1/2 ounce and 3/8 ounce spinnerbait what willow size is recommended? 

I'm looking at putting a few together for my KY lake trip.

#5 and smaller. Front blade would be 2 sizes smaller if you're making a tandem.

Typically you would see a #4 1/2 rear blade and a #3 front blade on a 3/8 oz for a tandem and a #5 rear blade & a #3 front blade on a 1/2 oz bait.

I've gotten away with a #5 rear blade on a 3/8oz tandem.

EDIT: I use this as a guide:

http://www.jannsnetcraft.com/content/make_spinnerbaits.htm

Depends on what you are trying to accomplish?

Most factory 3/8oz baits will have a 3.5 or 4 front willow and 4.5 rear. The 1/2oz will be 4 and 5 for blade sizes. The baits I make I like smaller blades and will use 3.5 and 4 willows on both sizes. Around here we fish a lot of clear water and there are a lot of SM. Big blades rarely work unless it is the fall but compact baits seem to work. Let me know if you can use some 3/8oz hidden weight heads as I have some built on 1/4oz super stainless frames I could trade.

Allen

Thanks guys.  That hidden eye might be neat.  I'm going to check some of them out and see what they look like.

Thanks Jigfishn10 for the chart.

Good luck @ KY Lake.

If you down size your blades it will allow you to burn the bait without the bait rolling over. I think some of mine I burn have a # 2 and # 3 blade on 3/8 oz head.