Hewes reels have thicker wire and do indeed sit taller than standard reels. I've never met a single-reel tank they didn't fit in, but indeed the multi-reel tanks can be a problem. But here's where Nikor's infamous "every tank is a unique creation" problem can be a benefit - you can eventually find one that will accomodate your reels! I have 2-reel and 4-reel Nikor tanks that can handle that number of Hewes reels. The two different Nikor lid-pour systems play a part too. One hangs down more than the other and can affect how many Hewes reels will fit. With tanks so cheap these days you can either buy a few until you get a good one... or ask ebay sellers, say, for precise measurements of tank height and compare to the one you have that's too short.
Duncan