Depends on your spot meter - Which one do you have? Spot meters often don't handle quite as low an EV as an incident meter will, but good ones are plenty capable. I'd actually meter for your mid-tone, just as you would in daylight. Your highlights are going to blow out regardless, but you can handle that with development compensation. And totally disregard the advice to use a DSLR as a metering substitute - DSLRs A: do not have reciprocity, so beyond 1 second they won't show you proper exposure calculation, B: DSLR sensors do NOT map to ASA/ISO settings - Changing the ISO setting on a DSLR will change sensitivity up or down, along with the concurrent noise level, but they don't match film sensitivity! Try this if you don't believe me - set up a still life subject in the studio using strobes. Set your flash meter to ISO 200. Set the DSLR to ISO 200. Take a meter reading with the flash meter. Set the DSLR to that setting, and expose it. When you chimp, you'll find the image on the LCD will be off - it will depend from camera to camera which direction it's off. Try it with a different DSLR - you'll find the settings are also off, quite possibly in a different direction! Usually it's less than a full stop, but sometimes it is more. Negative films have enough latitude they can handle a one stop variation and remain printable, but to say that ISO 200 varies by up to 1.5 stops from ISO 200 means that it's not ISO 200. Remember that ISO stands for International STANDARDS Organization - it's a standard that is supposed to be absolute.
Back to the context of the original post, when you couple the ISO of the DSLR being non-standard with the absence of reciprocity in digital photography, if you base your exposure settings on what the DSLR says, you can find yourself way off on the exposure and have really dark, contrasty negatives with no shadow and minimal mid-tone detail, or in the other direction, plenty of mid-tone detail but blown beyond compensation highlights.
To the OP: How are you planning to develop the film? My personal approach with HP5+ would be to set the meter to ISO 200, expose for the midtones, and develop at an N- to keep the highlights under control. Meter the highlights to see how far apart they are from your midtones to know how much N- development to give. N-2 would be a good starting point if you must do it by guess.