Funny you should say that----I've got three like that----
2 with a self-modified backplate, and one with a nice(but a bit pricey) purpose-machined Aussie one---& all 3 using old OS pumps---one 140,one RFP61,And one Hanno.
All use the old RFP type 86 carb,with the return to the pump blocked off for simplified plumbing.
And all are shimmed out 35-40 thou...gives a few more revs and softens the sound nicely(does that qualify as "internal mods"?)
They all do 8300-8400 on 15 nitro, on an APC 17/12(so a few more than the YS 160 on 30), and idle easily at 1700-1800(or less if you wish),and transition nicely and consistently once the carb has been set, and a bit of fancy throttle curving has been done.
BUT,in flight, they aren't quiteas easy or forgiving as the YS 160 to use,so,at the top levels, they're not quite there....

Edited to add---and a stainless rear bearing....