I ride a Diamondback Trace Comp, https://www.rei.com/rei-garage/produ...comp-bike-2017 . Changed the flat handlebars to drops, this made a huge difference for me in fit, comfort and handling of the bike.

The bicycle comes with a Suntour NVX-HLO suspension fork, 75mm travel. The fork is a version of this one Details - SR SUNTOUR Cycling

I'm feeling like changing the fork for a rigid carbon fork. I ride with the suspension locked, thus I have no need for a suspension fork of almost 6 pounds, plus the carbon might make for a smoother ride.

I have my eyes on this fork: https://www.ebay.com/itm/1-1-8-MTB-B...r=541738484442 , the tapered version as the axle to crown length is the same as my current fork.

I still have to confirm though that the current fork is tapered. I believe it is, the head tube is tapered, I just haven't felt like taking off the stem to look at the tube.

My question is:

Should I be looking at a fork with an axle to crown length as close as possible to the current since I ride with the suspension locked or do I have to calculate the length based on some give on the suspension? Information I've found on this is all over the place, can't quite get a straight answer searching older threads.

*I'm already saving up for another bicycle, please no "save money for another bicycle' answers.
**The weight difference is secondary, not really playing a part on my decision, although a lighter bicycle would be nice since I have to carry it up and down four flights of stairs every day.