My original merlin came with rigid forks. I've always used rigids. But I've considered putting on some older short travel zocchis to make life easier on my wrists. do I A) Buy some and try or b) measure somehow? Naturally I want it to keep its darty nimble handling and not turn into a slack-angled DH compromised mess.
I'd have thought this was the sort of thing the STW oracle would know/tell me in a heartbeat!
measure the original rigid forks axle to crown, the SAGGED axle to crown height of sus forks will give the same geometry
i've done this with old steel frames with some success.
Can you not put a bigger tyre on the front and run it a bit softer? This would give you some comfort without slackening the angles.
I've got a 93 kona explosif with rigid p2's (no sus correction), even putting 93 rockshocks on (60mm travel i think) makes it feel wonky.
Also try some big n squidgy foam grips.