OP, if you want to give Chasteberry a try, I’ve had good luck with Su-Per Chasteberry liquid from Gateway for my pre-PPID, IR, PPSM drafty cross. He gets a 2 ounce shot glass per day of the stuff in his morning grain. I can’t speak to the Smartpak pellets, they may be excellent but I haven’t tried them. I did try human gel caps w/ Chasteberry powder but then I read an article somewhere that mentioned that the liquid versions may be more bioavailable. I worked with my Vet and looked at the Evitex label to determine dose. Here’s the link to what I use in case you want to take a look.
https://www.su-perstore.com/m7/sfechaste--su-per-chasteberry-liquid.html
Oh, you might also want to talk to the Resvantage folks. I give Resvantage to my guy as well and the two combined have really worked well for him. My vet wants to hold off on Prascend for as long as we can for my big guy but he also has perfect feet so we have that going for us.
My mare is on Prascend and took a long time to adjust to it. We have settled on a 1/2 pill every other day and will test her ACTH levels this fall to decide if we want to adjust that for the winter. She’s an odd one, her ACTH was at 55 this spring with no symptoms of PPID. To make things a bit more unusual, her insulin was below normal which ruled out using Chasteberry because that can lower insulin levels and her’s are already lower than we’d like. I may consider switching to pergolide for her if we have to look at raising her Prascend dose. She acted as if she were sedated when we tried a higher dose earlier this year.