WE have a fantastic Trigano 6 man canvas frame tent which has withstood high winds and torrential rain.
the only problem is that it does not have inbuilt ground sheet so when we set it up, there is always a gap at the bottom . Storm flaps designed to come inside. the elastic has been replaced on all fixing points around bottom of tent several times over last 14 years, but it is never able to bring the tent completely in contact with the ground. subsequently we get a lot of wind comming through from under the edges and it gets very cold.
We had a Lichfield frame tent that had the same problem which we overcame by pushing the leg bottoms into the ground by the required amount. If the ground was too hard to push the legs into we used a large tent peg to create the hole.
Do the storm flaps reach the ground? If so, you could peg through them when you put the groundsheet in, to keep the flaps down & block the gap.
If even the flaps don't reach the ground, you could remove the spike in the bottom of the leg poles & saw off an inch or more, file, then replace the spikes.
you could try and stretch the canvas?
Erect in garden, use water (no detergent) soak through and stretch, allow to dry and redo until back to normal. The toy can re water proof it.
We have done this and gained the 3 inches that our canvas tent had shrunk by,
------------- 2015:
Easter Weekend - Northern Farm Burnham
March/April - Dolgamedd Wales (Tent)
May: Paris/DLP
June - Twilite Leisure Park
July - Germany Black Forest
August - UK
New Vango Orchy 500 to try STILL! STILL!