A couple comments
Thank you for taking the time to comment. As I am also putting a ULPower 350iS on the 12, I am glad to get your input. Based on the thread, "properly equipped" means 1) Heated Pitot 2) Autopilot and 3) TSO'd navigation source with a 4) sign off on the pitot static system.
You're welcome. I agree with having a heated pitot, AP and pitot/static check, 91.411, and then there is also a separate check for the transponder, 91.413 that is required. I would also include the items listed in 91.205(c) for night flying, which I do often. And then there is everything by 91.205(d) that will be required by operating limits as well. All of that, meets my definition of "properly equipped".
I personally have a GTN625 , which is TSO'd under C146, which is the WAAS TSO; it's a fine unit and I recommend it. I see Van's is now offering a similar avionics package for IFR training. However, you can fly IFR with a GPS TSO'd under C129 (non-WAAS) with some restrictions. You cannot fly IFR with a non-TSO'd GPS using that as your primary means of navigation - but that is way off topic and already discussed at length in other threads.
Prior to entering any form of precipitation and OAT is <=45ºF, I turn on my pitot heat. Thermal layers can change quickly in IMC and ice may form, so I recommend having the heated probe, and use it.
A pro-tip for Garmin G3X users is that the regulated GAP 26 probe has a discrete output that can be configured to alert you when OAT is <45º and your probe temp is less than 77ºF and/or your power to the probe is off; a very nice feature.
My definition of a good IFR airplane is one that is stable so you can spend 10 or 15 seconds looking at a chart and when you look up everything still looks good on the AI. My Cherokee is like that and very stable. The RV-12 has an empty weight half of the Cherokee so it gets pushed around more and seems a little less hands off stable. I would recommend the AP if you are serious about flying the RV-12 in IMC.
Getting "pushed around" isn't just about gross weight, but includes wing surface area for wing loading determination - the higher the wing loading, the less the plane will be affected by thermal activity. Depending on which Cherokee you have, the wing loading at gross weight has about 13.4 pounds per square foot (2150lbs / 160 sqft), whereas the E-LSA RV-12 has 1320 pounds and 127 sqft for 10.4 lbs/sqft. Three pounds is a difference, but not so much that I would say it gets pushed around noticeably more than my brother's warrior, that I've flown on the same day, in the same conditions. For comparison a B58 Baron is 27 lbs/sqft, which is significantly different, or a 747 which has about 133 lbs/sqft. When trimmed out, an RV-12 is quite stable and an excellent IFR training platform, IMHO, although I wholeheartedly agree with having an AP - not for stability, but for flying IFR single pilot.
P.S. Congrats R7237 on the UL350iS install. I'm happy to share my lessons learned or just compare notes if you want.
EDIT: I just remembered, my 12 has fuel out in the wings, not in the baggage, which may contribute to its stability more so than fuel at the centerline.