yeah i ran locked diffs in my speedway minis for years & years,,, they work good BUT!!! we didn`t do the "Usual" weld it all up" trick
we "oxy-welded" just the valleys in the exposed planetary gears sections,,, so,,, in effect, you could pull the diff apart (as per normal) then fit the new (welded-up) planetary gears,,, & bung it all back together
so,,, this gave it a tiny bit of play,,, which turned into more play the more you drove it, because the teeth beside the welded sections would "bite" into the oxy welded sections & allow a bit more & more play, (to a point) bcause the oxy weld is soft,,, now i certainly don`t recomend arc welding them, becasue that`s too hard & bits will "chip-off" & then float around in your box,,, & that wouldn`t be nice right?????
now oxy welding diffs this way was pretty good for in the pits etc (tight turns) because it gave us a little bit of forward & aft play... But also made it pretty easy to fix "IF" we busted an inner axle... then it is just a simple swap out the inner axles as per normal & re-fit the welded planetary gears back in

easy-peasy
But,,, i certainly wouldn`t recomend it for tarmac/bitumen,,, i ran one of our sports sedans at Lakeside with locked diff in it, a few times, & it wasn`t nice,,, do-able & grippy,,, just not nice, & yes tiring, & wears tyres a fair bit quicker than slippery diffs do
just be careful they don`t bite you & bitch-slap you,,,--> you will need to take charge of the steering & throttle --> DON`T let it take charge of you

I`ve had a pile of people come back from driving locked diff minis , shaking like a leaf ... very sweaty hands... more than a little red with embarasment,,, & also with decent sized dents in the wheels from being "Pulled" into a gutter
so,,, if you`re going to do it, then yep they`re cool for the dirt, but remember to simply "Take-Charge" & do it with confidence,,, or they can/will bite you

if you`re doing it on the tarmac then it`s a just the same except a bit harder on the arms & rips your tyres pretty quick