Interior Window Trim

Greetings again. I wondered if those of you who have done fully tear out of windows where you replace all of the interior trim could weigh in on something. We are getting Marvin Wood-Ultrex windows installed. We can either order them with the jamb extension or not.

Currently, our interior trim is the picture frame type (not sure if that is what it is really called) where the jamb extension is simply surrounded with textured trim. My better half wants stool and apron type sill. If any of you have done this, how was it done? Did you order the window without the jamb extensions or did you order it with the sill jamb extension longer and cut it down on site? Any advise would be appreciated.

Thanks again to everyone in advance.

I order them without extension jambs. After the stool is installed/nailed to the bottom 2x, then the stops are shimmed and nailed on the 2 sides and top. Then the casing and apron is nailed on to finish the job.

I would order the window with JE applied to top and two sides.
Install window, foam etc.
install dog eared stool.
Install vertical leg trim, install head trim.
install apron with coped, routed, or end caped returns.

Thanks for the information. I had the understanding that the wood-ultrex in the Marvin Integrity could not be ordered without the extension jambs. I may have been misinformed though. I will double check and thanks again for the help!

You will need to check with your supplier and see what the JE options are.
I like the JE applied because I do not typically use a nailing fin to install. Because it is easier to make the control point of the JE lining up flush with the wall so that your interior casing will lay flat. Also since most of our exterior finishing is in trim coil it allows use to make adjustments to the total projection, that or the use of flat composite trim.
You can go the other way by setting the window with a fin and then apply JE. You will probably need to rip your own stock and some perhaps on a bias, then you have to apply it consistently and not shoot a nail through the balance system.
Also you can install with fin and JE applied and control flushing up the jamb and wall by shimming/packing out the back of the fin.