Your writing is elegant and flowing, and I'm envious of the inks and pens you used.
Here is some constructive feedback. Even if my words don't show it, imagine them written in the gentlest tones possible
The most straightforward method to improve the legibility is to simply shorten the lead-in lines to the 'i's and 't's. With the existing longer and steeply curved lead-ins, the mind is tricked into reading 'in' as 'un', 'if' as 'uf', 'that' as 'what', 'to' as 'ut' or 'uto', and even 'user' as 'wuser' (Waterman sample, Line 2). Even though the mind is confused for only a split second (as words like 'uf' and 'uto' don't make sense), seeing these strange letterforms multiple times makes the reading process less smooth.
The dots to the 'i's are sometimes too far from the stem ('is', Line 2) or missing ('uphill', Line 5).
The crossbars to some of the 't's may be slightly too high. I like high crossbars and you may be using them intentionally as part of your style. Just be aware that some words may be harder to recognize if they contain both 't's and 'i's with highly-placed crossbars and dots. ('With' is an example of such a word.)
I can tell that you are more comfortable with the flex Waterman than the Monteverde. Since the Monteverde (now) has a cursive italic nib, it will shine when used to write cursive italic. (
Sample.). You can still use it to write in your current hand--which is closer to a strongly modified swash-heavy Palmer (which I do like!)--but note that italic nibs often require more internal and counter space (the space within and between letters) for legibility. As an example, the 'e's written with the Monteverde often have closed loops and resemble undotted 'i's.
Lest you think the above criticism is too much, let me assure you that most of the letterforms are well-formed. In fact, especially in the Waterman sample, the 'W' in 'Waterman', the 'f's, the 'g's in 'behaving' and 'letter-writing', and that extended lead-in for 'S' in 'So' are very creative yet legible. The lowercase 'r's are perfect, the fancy capital 'R' in 'Remember' is gorgeous, and the 'w's in the bottom of the sample are especially nice.
If you do decide to practice Copperplate, it's best to practice slowly. 'Fast Copperplate' is an oxymoron. If you want to improve your existing hand without sacrificing too much speed, you can focus first on shortening or widening out the lead-in strokes and paying more attention to the 'i's and 't's.
Thanks for showing us your beautiful hand!