@Adson...correct on both counts.
Enlarging the progress bar is controlled by MusicBee but does not work with the style of graphics or their method of implementation used in my skins. Unfortunately it's a trade off between the look I want to achieve and an (optional) function (or two).
Similarly it's not possible to make a wavebar active in every skin I produce. That is a matter of my choice but based on logic. Let me explain using C90 as an example.
The 'screen' area in this skin is shown as being in the top half of the player body. That's because I've made it look that way for the sake of the design/aesthetics. However, to place a waverbar in the player, MusicBee considers the whole player height to be the screen and places the wavebar vertically centre. There are parameters that I can set to control placement, just like a button or text, but with a waverbar these parameters are overridden by MB and it places it as described. So I can put it anywhere I like left to right, but up or down is always 'middle for diddle'. In this case, totally obliterating the image.
I believe that this override was put in place some time ago for a very valid purpose but until it becomes available for independent positioning it's another trade off...either every skin has to have a full height screen or some can have a more 'unique' appearance and no wavebar.
A bit long-winded I know, but I hope it clarifies why certain things are done certain ways.