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Thumbers can be thrown with any disc, but the results will vary greatly, as they should. Most people I've seen, use the thumber to get out of trouble or to go over objects. In which case, something over stable in about a speed 7 to 10 ought to do the trick.
Now if you want to start shaping shots, throwing for distance, skipping, and sliding your discs, you'll want to start try ing other discs. You'll also want start trying different release angle with your shots to see what happens. Gotta get out and throw em to see, or I'll be writing all day. Here is my list of discs I use to thumb.
Gummy Champ Firebird- Acurate 300ft bomber, 175g to smash through leaves and branches
Gummy Champ FL- Acurate 300ft++ bomber, 153g freakishly over stable open field driver
Lat64 Opto Striker- 175-250ft tunnel shot, skip shot 174g stable
Lat64 Opto Pain- 100-240ft slow big side angle entrance shots (You'll just have to try it) 176g over stable