I bought the Sunpie in late 2017 for my new 2018 Streetglide Special and it gave me issues to make it work also but I believe I was also adding the visor black trim ring at the same time. I made it/them both work with only minor aggravation and it/they are still on the bike working fine over the last almost 7 years.

 

This is a pic of the setup of the light bucket on my '09.
If I were to loosen the two bolts for the windshield mount and the acorn nut beside the tach on one side fo the bike, would that allow me to open up the nacelle a bit? If this would work, it might allow me to get the mounting plate in where it should be.
I'm guessing I would also have to loosen the top chrome spear as well.

 

Does your bucket not have a relief at the 12 o’clock position like it does at the 3 o’clock position?There’s a YouTube video of a SunPie being installed and his bucket has a relief cut where the springs are at.

 

That's not going to work on a RK nacelle... It fits as expected in the batwing fairing, but not the RK.
I recommend comparing the factory ring to the aftermarket and see if the OEM ring can be made to fit the new headlight.

I'm a huge fan of the Sunpie lights, and as I have said a million times, the Sunpie LED headlight is the absolute best value in the 7", LED headlight market.

 

I only have the relief area at the 12 o'clock position but I need the same thing at the 3 and 9 o'clock positions or I will have to grind off part of the flange at the bottom of the spring on one side. The dots in the pic show where I would need to grind it in order to fit it inside the headlight.

 

I did look at the OEM mounting ring to see if I could put it on the Sunpie light but it doesn't look like it will work. They mount in two different ways.
Do you know if the nacelle can be loosened on one side and opening up a bit to get a little more clearance to get the light in? I know it's not ideal, especially for later work in the headlight bucket, but I'd like to make this light fit if possible. If I loosened the three bolts shown, would that allow the side to be pulled open a bit or would I need to unbolt the entire thing?

 

I watched that video on YouTube and his headlight bucket has the relief areas at 3 and 9 o'clock that mine do not have. Bummer!

 

My 2019 FLHTP came with the Harley Daymaker LED headlight. The Sunpie trio I had on my 2002 ElectraGlide was better. The Harley LED had a huge dark spot between high and low beams.

Have the Sunpies in a box now as I am running the Custom Dynamics Adaptive II headlight.

 

I contacted Sunpie again and asked about return policy if I were to try grinding down one of the side flanges that makes it too wide to install the LED. I was told that even if the unit is not resalable if/when I return it they will still give me a refund. I don't run into too many companies out there who would do that.
Surprised me but at least now I can experiment to see if I can make the light work.

 

I made a last attempt to make the Sunpie headlight work - I took the LED out of the bracket that it shipped with and put it in the OEM bracket. It came real close but the three tabs would not quite align with the grooves for the tabs so the LED would not sit low enough in the bracket. It stuck out too far and was crooked. I attached pics for reference. I don't know if they make a unit that will fit the FLHP, but I'll ask again.
Thanks for all the help and advice.