If you dont lower the front proportionately, lowering the rear will effectively reduce the head angle and slow the steering a touch and make the bike a bit more stable.
Lowering both ends will keep the same geometry but change the centre of gravity which will also effect braking.
Just lowering the rear will put a little more weight over the rear so would presumably change the braking characteristics ....... whether this is a good or bad thing is probably down to personal preference.
Personally I reduced the front fork length of my baggy by 15mm to quicken the steering up a tad and put a bit more weight over the front wheel. I think this has improved the handling significantly ....but again this is probably just my preference.
Now I need to lower a baggy front and rear so the Mrs can get her feet down when I buy her one
hence my interest in whether these bones will fit. Not a big deal really as they will be simple enough to fabricate anyway.
Cheers