Macro with a 300 f4L IS

Since it a rainy day here on the west coast I thought I would figure out the best Macro setup for my 300 f4 by doing some test shots.I don't
have a external flash so I wasn't too worried about IQ.I wanted to see which combo of a 1.4 TC,2.0 TC and a 25mm Canon tube would be best.I
tried all combinationsand this is what I discovered.

As expected the TC's produced some slight degradation in IQ and of course the 1.4 was better.

On a 300mm lens a 25mm tube by itself has approx. the same "magnifying effect" as a 1.7 TC would have but of course no Infinity Focus.

Stacking the tube in between the lens and a TC(vs. the TC in the middle)
will provide additional "magnifying effect" at about a 1.2 X factor.

So for now it's the tube with the 1.4 having the tube in the middle but straight tubes are the way I'll go soon.

Not quite sure I understand this. You should get the highest mag when using ext tubes and a TC with the TC closest to the camera body ie camera>TC>Ext tube>Lens.

Brian v.