That looks terrific! Very disciplined, good eye for slant and spacing. I think you're absolutely ready to move on to the dip nib. Here are some things to be aware of when you do.
First, you'll want to start out with some of the beginning exercises to get a sense for how to create the shades evenly and smoothly, and transition nicely between thicks and thins. This will almost certainly require adjusting your grip and the way you hold the pen to align with the slant, because a monoline fountain pen can create nice letters no matter what angle the nib is with respect to the slant, while a flex/dip nib really does need to have the nib aligned parallel to the slant, so the tines split evenly for shades. Make sure you practice how this works, rather than just picking up a dip nib and trying to write with it.
When you do move onto the letters, you'll want to adjust your spacing, because shaded strokes are thicker than monoline strokes. The nice, evenly space letters that you produced with the fountain pen will look cramped if all the downstrokes are thickened. Also, the loops in your ascenders and descenders will need to be widened, for the same reason.
Finally, a few comments on the individual letter shapes, which you can fix just as easily, or more easily, when you are using the real dip nib:
-The final stroke of your n and m and p can be too curvy, concave rather than straight down and a final ending downturn. In "attempt" this is pretty clear with both "m" and "p", as well as the "n" in "watching". Your "p" is better in "pen" and your "n" is good in "strong".
-Similar to above, try to keep your straight strokes truly straight. In "a" sometimes the stem can get a big curved inward, as in the second "a" in "actually." This is something that gets more pronounced to the end of the page, because in the first two lines your "a"s are all pretty good, with nice straight stems.
-Remember to watch the slant! You're really, really good at this already -- better than me, certainly -- but sometimes you diverge a bit, as with the "h" in "watching".
-Try to make the connecting strokes join up with the next letter at the same height every time. Sometimes the join is at the top of the minim, as between your two "p"s in "copperplate" and sometimes it's much closer to the bottom, as with the "rp" in "copperplate". If they're at a constant height between all the letters you get this lovely sequence of pointy triangles in the counters along the baseline of your letters. If you cover up the top half of the minim line it looks like waves on an ocean when you do it right -- as you've got in the "actual" of actually.
-Even with the monoline nib your spacing can get cramped. For example, "this" on the second-to-last line, and "strong" on the last line.
In any case, carry on! Things may get more uneven when you add the new complexity of dip nib, and it might seem like you're regressing, but don't be discouraged. You have an excellent understanding of the letter forms already, and I think you'll be producing lovely copperplate before too long.
