I hope this doesn't sounds rude.
I will try to make this more clear. It seems that there is a typo somewhere.
I understand that you have 2 different types of material available:
CT2k.08 and CT5k.SOMETHING8
Seems to be a simple typo. Just trying to confirm which membrane thickness is on your CT5k material.
Mountainfitter website reads:
" Cuben Fiber CTF3 CT5K.08 1.50oz Sq Yard
CT5K.18 Cuben Fiber is the most common cuben fiber material used for Reinforcing Patches on Tarps and Tents since its super strong and highly abrasion resistant.. This material weighs 1.50oz per square yard and has a break strength of 190lbs/inch. Cuben Fiber is a translucent material. Color is Standard Gray. "
The sale price on the yellow CT2k.08 is quite nice.