So I've picked one of the designs from the last post and tried to continue designing the form. The attached image shows what I have. This is the point where I would like to be doing it in a digital format. Then I could drag the different parts around and create multiple designs quickly. That and it would be far easier to read than trying to read my terrible hand writing. I just don't write enough these days for it to improve. I can type so much faster.
So I may try and find an application I can use for faster and clearer designing of the forms.
As for this design; I'm not sure how to lay out the buttons in the middle. I could always put the format dropdown lists next to the input and output labels. I had also thought about adding some arrows to make the conversion direction more obvious. A couple of buttons I've not added here that I plan on including are ones to swap the format selection and contents of the text boxes.
Also if you have not guessed already I don't have a scanner available so I took pictures of these with my phone camera. Another reason for digital format is that it's easier to make copies and upload them :).