I understand about the cooling 4 fin vs 8 fin. But clipping is happening right away.
i too used an old 4 fin junker...i build an extra set of fins to boost cooling ....
i replaced the original rectifier to a bigger one that joe recommended....
i used white oaks power supply cap upgrade....
my transformer/rectifier setup gives be a full +-82v....more than enough to drive to full power...
i did use the white oak chassis because my junker did not have top and bottom plates and i wanted the improved power socket and extras included with the heavier chassis....
sniff recommends these aircom cooling fans for heavy use...
https://www.ebay.com/itm/3325218315...aeJ5BixoJKUEDXeononl/KBPpTkk|tkp:BFBM2ITV5dpg
i have not done so yet....as i will build a new enclosure for my systems...and incorporate a cooling system when the time comes...
but, i dont push mine over 110 db....a little better than half way using schiit modi3 dacs with schiit magni 3+ and heresy preamps...
thats plenty loud enough for me...