I found a over size IKEA Trippevals blinds for $25. Normally, these suckers sell for $65 for large windows. I needed to trim 5", so it's definitely worth it.
Step 1: Remove End Caps.
These instructions are good for 48" x 76", cutting 5" to fit 33" window width. There are springs & pulleys to be disassemble, be warned ...
First is to remove the end cape from spring end. Take a screw driver and pry off the locking tabs. Use needle nose pliers & unhook the spring.
Step 2: Drill Out Rivets & Remove Spring Anchor
Take a small 1/16" bit, drill thru the 2 rivets & hammer out the mushroom head rivets, be careful not to break the plastics
Step 3: Remove Bottom Caps Also
Also remove the bottom end cap, there's a small metal weight inside also. Try to remove it, or push it further down (with stiff wire...etc..) so saw blades wouldn't hit it.
Step 4: Measure & Cut
Duct tape the cut end to reduce flying metals. Use whatever metal blades or hack saw.
Step 5: Reattach Spring Anchor
Measure & drill new holes for the plastic anchor. Allow for 1/2" for end cap. Attach with machine screws, and a nut & washer if avail. New position should still be ahead of the draw string holes.
Step 6: Reduce String Slacks.
I did it the stupid, harder way, but here it is ...
After cutting & spring removal, I found shade off balance & too many string slacks. So I remove the top header, slide it back in with the 2 strings inside the channel. Using needle pliers again, Reduce the string slacks as I slide in.
In hindsight, I could've just remove the bottom and re-tie the damn strings ... sigh ..
Step 7: Reattach End Caps
Cut off the locking tab if needed, put everything back,
Step 8: Final Mounting.
This step varies depending on your existing window. Mine was a bath room with granite sills and very nice Anderson window & trims (previous owner was nuts). Too lazy to drill thru stones, so I make some 1x3" blocks just for the mounts. Can't see them once shades are up anyway.
Use whatever unobtrusive mounting you like