Balsa thickness?

After getting my first SR from Wid (very happy with it) I'm looking forward to making my first balsa strop. I plan to glue two pieces of balsa to a block of wood and then put CrOx on one side and another abrasive paste on the other. What should be the thickness of balsa sheets? Will 1/3" be enough or should I go for something thicker? Balsa is very hard to find here in Bulgaria and prices are a bit on the high side so I don't have much choice.

no clue as to what 1/3 means, 1/8 inch works well

Sorry, I'm not used to using inches. 1/3 inch should be 8-9mm while 1/8 is ~3mm, i.e. I should be able to find balsa pieces that I can use.