I have 2 Harris 25" extendables. one is on my 30-06....03-A3, and the other is on my 223 NEF bull barrel. I have had them for 6 years and i love them. They work really well in the sitting position fully extended or just one section out for bench stuff. I got them through ...Cheaper than dirt .com
You want the 25 inch model if you want to sit or shoot in steep or bushy conditions, 27 inch if you are taller. I had the 13 inch model and it was pretty much worthless unless I was in a flat field.
When it comes to scent, there are basically two types; those that attract and those that mask. I've tried both on many occasions. There are lots and lots of "doe in heat" scents, designed to attract a big buck into range. I've also used a "cow in heat" scent while elk hunting.
Another scent would almost be better named as a "coverup smell". The main goal is to cover up human odor or mask it. Though I don't believe you can ever totally eliminate all human...