Luckily, a good friend of mine - Andy Hennessy, in Ireland - had a D1 spring and sent it to me free of charge. Now, that's what ytou call a good friend! Thank you so much, Andy, for your kindness - I look forward to you keeping in touch with progress on your D3. A picture would be good, too!
Talking of pictures, you can see the difference in the springs in the above image: top, D1; bottom, D7. Quite a difference in length, no wonder my stand wouldn't lift!