No, SS1 isn't that big, but SS2 might be.
SS is at least 40× given Goku vs 50% Frieza. Frieza in Final Form should be Star level range, given the huge gap between his True form and first form. Trunks one shots Frieza, they train, train again in Hyperbolic Time Chamber...
I guess you're right. That means that they have to be Large Star+ in base to preserve the multiplier low-ends. So...
Edit: Just did a bunch of thinking. In Short: Frieza in First form= Dwarf Star+ bordering on Small Star. Small Star and Star have about a x50 difference, making Frieza Star level because Goku should be stronger than 2-3 form Frieza who should be at least Small star. Trunks then one shots Mecha Frieza, who is confirmed to be stronger than regular FF Frieza to an unknown and likely small degree, and Goku shames Trunks by making his finger hard enough to block the Sword swing that cut up a being who can survive a planet exploding on their unconscious body. That same Trunks was cucked by the lovely #18 who after breaking his new SS Dad's arm, who should be stronger than Goku was when he came back to Earth, broke his sword by casually putting her arm up. Star level is x2.2 times wide from high to low, so she should be at least baseline Large Star, and this ignores the training that Trunks might have gotten, if any. They go into the time Chambers and come out stomping characters who stomped the Androids two fold-- Imperfect Cell stomped Kamiccolo and then Semi-Perfect Cell, who was comparable to Imperfect Cell, was stomped by him. This should make their bases At least Small Star Level+, likely Star off of that, since assuming anything bigger for basic super Saiyan than a x40-50 increase is wank for Frieza basically. Imperfect Cell should be 2x stronger than Kamiccolo, and then 2x stronger than himself/16 as Semi-Perfect, meaning he is a 4x beyond basic Large Star bare minimum. Then, Cell stomps Vegeta, who stomped him earlier, meaning a suppressed perfect Cell is 6x stronger than the Androids. Cell Games, and covering what Mastered Super Saiyan really is. The transformation shouldn't really be any different than the initial form, considering all they really did was make it so that it doesn't drain their stamina to be in it as much as it use to-- kind of making it like a second base. It was their training that made them so much stronger. If anything, it seems that SS2 is the one with the massive increase, because their bases would be Small Star plus mathematically with these assumptions, though I doubt that they wouldn't be at least regular Star level at this point, due to how much I low-balled them with this scalling.