How would you work the fastball special?

[Shadowbane13]

First some background;
I am a hafling rogue arcane trickster that dual wields short swords
My party consists of:
Gnome artificier
Hafling swashbuckler
Human fighter
And me

So we were fighting this weird creature (I think my DM improvs a lot) that's clung to the wall about 5 feet up. Me being a small creature decided to work with our human fighter to do wolverine's fastball special. The dice gods were on our side as the DM let the shenanigans fly. Fighter picked me up to throw and rolls a nat 19 for strength check. DM says he's able to toss me with great power at the enemy. I have both swords out and because of the fighters roll my DM says to roll for both attacks to land as normal and grant my sneak attack because it is an unpredicted attack. He also says that any natural roll above 18 will classify as a critical due to the strength roll. I roll a natural 17 and 19 with sneak attack on my second roll. So being level 3 I was granted 7d6 for damage. (1d6 for first attack, 2d6 for second attack crit, 4d6 for sneak attack crit). With finesse weapons I get my dex of +3 to damage so I ended up rolling 30 damage. Brutally murdering the creature. Was eventful and fun. Just
Wondering how others may have handled that as fellow dms. I myself would have done probably something similar.

[Armored Walrus]

I like it. I probably wouldn't have thought fast enough to grant the widened crit range due to the STR roll being so high, but other than that I probably would have rolled with it fairly similarly to this.

[MrWesson22]

It definitely fits the Rule of Cool, so yeah, let it ride. That said, I probably would have either granted advantage or bonus damage on attacks instead of a straight up increased crit range.