Well to play devils advocate was any of the issues with the Collins class to do with up-scaling a prior design?

Most of them stem from that.

Major issues as far as I can see were:

1) Defective welding

Specifically the parts of HMAS Collins fabricated by Kockums

2) Noise due to the nose being changed to accommodate a different sonar, model tests were done with the old design but not revised when the changes were made to sonar fit

Also related to the scaling up of the design.

3) Propulsion system

Related to scaling up the design. In order to get enough generating capacity to get the required charging rate an extra engine had to be shoehorned in, with a clean sheet design the engine room size constraints may have been avoidable.

4) Periscopes and masts – RAN requesting a dubious redesign of the periscope from base design to allow the optical view when the scope was raised

No comment.

5) CMS – the biggest problem in many ways and utterly avoidable if they had gone for an off the shelf system (as they did in the end)

A beyond state of the art CMS when the project began that was never worked out completely and ended up obsolescent. Rectified through refitting with the Virginia class CMS.

Aside from point 2 none of these issues are due to scaling up the design and I would argue point 2 was utterly avoidable if they had done hydrodynamic model testing of the redesigned hull.

You sure about that?

Scaling up and scaling down submarines is a fairly common process and if managed properly should not throw up too many issues.

Not to the extent that it was done with Collins. Collins was three times the displacement of the original base design. The largest displacement of the Type 209 submarine was by comparison 50% heavier then the lightest displacement varient.

Edit: @ Pioneer, more spacing please!! Wall of text = not cool.