I am keen to modify my wherry in this way, and await answers from active-tools.com re their adjustable size rowing shoes which seem to come with individual backing plates/fastenings. I am hoping that these can be screwed to existing wooden stretchers without cups.

Other rowing shoe suppliers appear on google but less clear info about attaching them, as foot stretcher may be supplied by boat manufacturer?

 I assume that you have looked at fixing trainer type shoe through sole (under footbed to protect foot)?

I would suggest that you call Alden Boats 978.263.9010 (who now employ Gary Piantesdosi and force him to produce his rigs).  You can probably talk to Gary directly and get advice straight from the designer's mouth.  I'm sure he has a solution.

I believe you would only need remove the heelcups on the clogs and drill them to accept the screws that typically are used to mount rowing shoes. 

I understand from the supplier that the adjustable size rowing shoe from www.active-tools.com costing $90, I believe, will fit the rig and come with a template for drilling etc. Also sized mens and ladies rowing shoes from H2OROW Ltd are available which can be fitted either with their template and 4 screws or a single bolt if preferred. Cosing about $50 I believe. www.h2row.net. I think I will try the latter! Both are very helpful.

Not being entirely facetious here, but why not screw an old pair of sneakers to the Piantedosi wooden footbraces?

I have just fitted pre drilled H2ORow shoes with single bolt they provide to the Piantedosi rig wooden foot stretchers. The result is a fantastic success, and makes a mssive improvement for an outlay of $50.

ramjam, Fantastic news. Any pictures I can see?