If Urbestfriend could offer a comment on springs. If the spring they sent fit, then you should have no major issues.
Compression or Extension Springs are an interesting science. There's wire diameter, coil spacing, coil
diameter and spring length that are all part of a spring equation. Urbestfriend is an engineer and periodically
chooses springs for a design he may be working on. All the pre-mentioned factors all add up to spring rate
(load the spring will support at a certain load or length. Not sure which way you wanted to go up / down,
but this is likely what's happened.
