Illustrator: wave background with custom defined strokes

Question

Following this technique, I am trying to define the stroke ends of the below resulted pattern, but without luck.

What I've done so far:
- I've put a letter over the wavy strokes group (wave pattern created using the Blending option) > Selected all artworks, then Object > Clipping Mask > Make.
- Using the Stroke Panel, I've tried to modify the endpoint shape of the lines but it looks like it's not a properly way to do it, there is no effect displayed .

Is there any way to achieve the above mentioned effect? Thank you,

LE: I've managed somehow like this:
- I've created the line pattern using Blend option
- Expand
- I've Created a new (type) layer
- Type > Create Outlines
- Select All > Shape Builder > Deleted (trimmed) unnecessarily strokes.

The only question that remain, is how to achieve the round strokes ends inside the letter (as we can see, at this phase the Illustrator will make them round outside the letter (outside the outline).

Answer 1

The trick is to use Offset Path on your crop shape. This creates a new shape which you use to trim the blend.

It's a similar set of steps to those you already have:

1. Create your blend and expand it
2. Type your letter and convert it to outlines (this is your “crop shape”)
3. Use Offset Path on your crop shape (Object menu > Path > Offset Path…)
4. Use a negative value to create a copy of your object that is smaller than your crop shape. You should now have three layers: the blend, your crop shape, and your smaller offset shape.
5. Select your offset shape and your blend (and not your crop shape), and use Shape Builder to remove the protruding lines
6. Hide/delete the offset shape, leaving your original crop shape and the blend.

If you want the rounded path ends to touch your crop shape, when you are using Offset Path, set an offset value that is half your stroke width.