at the end of the day it is what you think is best. i have just tried to bring out what i thought was your vision, the pump needed to be given fair due and the overall theme needed considering with the elements in the picture. if you like the slabs the way they are then iy means you really like them that way and you will not be swayed by anothers influence (or bright idea) and so this aspect of your vision is confirmed by you, and that is what counts. framing and sucj i think you may understand a little better now or it might just have neen a case of ,'when you live with something often we see what we want to see and miss things others see'. i think lighting is very important in this piece and also i think what is important is the finished product, if that means layering inPS or compoiting somewhere so be it. its about the image rather than the teqhnique.
as i said, i tossed up about mashing your piece (im hopeless in PS) and thought that this would give you the option to make a firm desicion about the grass and what not.
i hope you are not too possessive of your work, its like i write a peice for a film and it comes back as a jigsaw puzzle, i know some get upset but i really dont mind, it was in the pleasure of doing it rather than the exhibition.
i think you may be th same and enjoy the process. i
take it easy and life will be easy