Wildcat load development

[gunner72]

Looking for some opinions on load development for my new build. I just got my new rifle and custom dies for a rifle I'm going to try. It's a one off cal so there is no load for it in any of the data sites or books. It's basically a .375 Ruger case necked down to .358 which is very close to a .358 norma mag just a hair bigger. I'd like to try H1000 powder and 225 accubonds. The next closest that I Could find is .358 STA but that's a bigger case although they do have data for H1000. What I've been reading for the last while is to fill the case to the bottom of the neck and weigh the powder. Then try 70% of that number and try it. I did that and the case to the bottom of the neck holds 88.1grs. Multiplied that by .3 and subtracted from 88.1 and that gives me 61.6grs. The data for the 358 norma is comparable to the min loads and that case is a hair smaller in all dimensions. The brass will need to fire form a bit in the shoulders so I'll have to get the real results on the Chrony after the second load but just wondering what guys that know think of starting with that load.