At 40m distance with 5m of depth, you're talking inches rather than feet.
I have graphed it on a scaled drawing, and it really is very little.
One of the greatest myths in angling is that you lose yards off your distance by allowing a lead to sink on a tight line. Unless your venue is amazingly deep, you will not notice any loss of distance.
There is a trigonometry formula for this, but I can't find it at the moment.
Of course, a bigger concern is that when casting a feeder to a clip, the feeder can spring back against the rod tip, in which case you will end up with the feeder landing far closer to you than you might have expected.