telltales

i'm a new Hobie Wave sailor - a few questions about tell tales.

The sail i have doesn't have tell tales on it. I'd like to stick some on. Any recommendations on how many to put on each side? where to put them? and what type/brand/where to buy?

and related - shroud tell tales - i have uses old cassette tape in the past, but it seems to come off easily with sail rubbing against it. What other materials do people use? are there any that you all purchase that are good?

appreciate any tips!

I bought from Sailrite once: https://www.sailrite.com/Air-Flow-Tell-Tales-Pack-14 and put them at the same locations as old ones were on my OEM sail: one at the front corner of the top plastic window, another - below the third batten from the bottom.