Joined: Jan 2010
Posts: 9,835
Likes: 1,816
From: Northern California
Bikes: Cheltenham-Pedersen racer, Boulder F/S Paris-Roubaix, Varsity racer, '52 Christophe, '62 Continental, '92 Merckx, '75 Limongi, '76 Presto, '72 Gitane SC, '71 Schwinn SS, etc.
Check to see how far that the existing spokes come up throughthe nipple's threaded bore.
Depending on how "long" (or short) that the existing spoking looks, will help to judge how much that the 1.5mm difference will make.
Your new rims might even be a better match for the existing spoking than the old ones, but I can't say without looking at the existing wheel and how far that the spokes come up into each nipple.