Stupice is a great tomato in cold places like Newfoundland and the mountains of Idaho (my zone 4 home). Look for the biggest blossom's for easier emasculation (and try using the tip of an exacto knife, works really well) If you like Stupice, you should try Jeff Casey's Maya and Sion's Airdrie Classic, it's a stable, great tasting, productive, early selection of Stupice x Suddith Brandywine. I've got a lot of breeding lines in F1 and F2 involving it as well as Stupice.
The lines are:
Stupice x Red Brandywine F2
Stupice x Purple Dog Creek F1
(Stupice x Red Brandywine)F1 x Amazon Chocolate F1
(Stupice x Red Brandywine)F1 x (Ernie's Plump x Sugary Pudovich) F1
(Stupice x Red Brandywine)F1 x Lillian's Yellow Heirloom F1
(Stupice x Red Brandywine)F1 x (Maya and Sion's x JD's Special C-Tex) F1
(Stupice x Red Brandywine)F1 x (Opalka x My Brandywine) F1
(Stupice x Red Brandywine)F1 x Sandul Moldovan F1
Maya and Sion's x Lillian's Yellow Heirloom F1
(Red Brandywine x Purple Russian) F1 x Maya and Sions. F1
(Maya and Sion's x JD's Special C-Tex) F2
Bianca Grande x (Maya and Sion's x JD's Special C-Tex) F1
Fred Limbaugh Potato Topx (Maya and Sion's x JD's Special C-Tex) F1
Gildo Pitroboni x (Maya and Sion's x JD's Special C-Tex) F1
Hege German Pink x (Maya and Sion's x JD's Special C-Tex) F1
A few photos:
Maya and Sion's Airdrie Classic
Maya and Sion's x JD's Special C-Tex F1
Oaxacan Jewel (just because it came up, and it's pretty). You should TOTALLY cross it to Stupice.
If you'd like seed from any of the above, I'd be happy to send them along.