If anyone has bought the 26mm of extension tubes, if you put them both on the 40-150mm lens @ 150mm you get focus range of about 80cm to 1.8m from object and really nice macro'ish shots.
Also don't have the problem with the silly shallow depth of field when using with prime so you can get a decent amount of object in focus...
Light might be a problem, but I think you can shoot like this hand held for insects etc
http://m43photo.blogspot.co.uk/2013/07/meike-macro-rings-highly-recommended.html
That lens already has a min focus distance of 90cm without the tubes. You sure it's not much less?