If you and I lift an object together, we're each essentially lifting half the weight, more or less (I'm sorry, I was tilting it more towards you to get the lighter load... won't happen again).
But cutting the DC to 10 for two and to 7 for three seems perhaps maybe almost too easy (ymmv). Of course, if everybody has to make a roll vs that DC, it might not be as easy as it sounds...
Reduce the DC by the number of 'extra' folk, and make one d20 roll adding all of their STR modifiers?
Gnome Boy (a.k.a. "Jon") • DCC play-tester @ DDC 35, Feb 2011. • Beta DL 2111, 7:00 AM PT, 8 June 11.Playing RPGs since 1977
• Quasi-occasional member of the Legion of 8th-Level Fighters.—Here Be DCC Monsters—VOORAK, L, Hunter, S10, A12, Sm10, P6, I13, L13, AC 10, HP 3, Spear +0 1d8, Init 0; R 0, F 0, W -1, Holy water, Pelt, 3 iron spikes, 1d ration, 4-leaf clover (Find secret doors) (+1), Com +1
SARKLA, C, Gatherer, S9, A14, Sm14, P15, I14, L8, AC 11, HP 4, Knife +0 1d4, Init 1, R 1, F 1, W 1, Chest, Basket of veggies, 2d ration, lg sack, waterskin, torch, Seventh son (Spell checks), Com +1
TARR, C, Hunter, S14, A11, Sm15, P13, I7, L7, AC 10, HP 3, Spear +1 1d8+1, Init 0, R 0, F 1, W 1, Holy water, Pelt, 4 torch, flint/steel, 1d ration, sm sack, Fox's cunning (traps), Com
TELVA, N, Herbalist, S13, A6, Sm9, P6, I12, L10, AC 9, HP 2, Club +1 1d4+1, Init -1, R -1, F 0, W -1, Chain 10', Herbs- 1 lb., 50' rope, 2d ration, torch, Speed of cobra (Init), Com