So what was everyone's preferred method for removing the gussets from rib number 5 in order to reinforce with 1/4" plywood? ...I should have visualized this better while I was reading ahead.  

**I wish the plans said something like -  make 18 ribs and then 2 more with reinforced 1/4 plywood" prior to gluing all gussets on these two ribs (rib #5).

I am thinking about buying a heat gun.  

When building them I had the fore sight to not  put them on : ) But other times I can be soooo stupid. Wont tell ya what I did yesterday.
In your case why remove with heat? Just cut away the majority of the gusset,leaving the part that is glued to the 1/4" stock.
Or hold a razor blade with vice grips, heat it with a propane torch and slip it under the gusset. So little thermal mass there is no concern of affecting the bond on the other side at the expense of needing to re-heat more often.

I do think that the plans are stupid for saying "Build 20 regular ribs.  Next step, build 2 of those 20 different."  I am more of a checklist guy and forgot about that step after working on ribs for months. I did not like how the parts fit around the squeeze out from previous glues on the root and tip ribs, as well as rib 5 so that is why I rebuiltmine.  If it's just rib 5, just remove the gusset and place in the supports, if it suits you.

I have fixed minor gusset errors using a sharpened painters 5-in-1, its like a stiffer putty knife.  I keep some sand paper stapled to a block of wood to keep it sharp for and glue trimming for squeeze outs or repair.  Super handy.

Thanks for the great input! I think I will start with that razor blade trick.

I tried the razor blade but it was burning the wood. David Cooper suggested a heat gun. This worked so well I wanted to share. Maybe it will help someone else someday.
I got them all off in under 10 min.
https://youtu.be/OUuPBH3yWyo

I has no problems burning wood with the razor, you must have got it a lot hotter. Watched your video and that does look pretty slick, cant wait to try it on my next screw up.

Wow, that worked really well.  Maybe I can salvage a few of my ribs with this method!  Thanks for posting the video.