This is my humble, yet well travelled experience when it comes to bivvies & shelter ... as it took me numerous purchases before i got it right for my circumstances.
Ok ... Bivvy first ...
I think the Force 8 Bivvies are a pretty poor effort by TFG, i havent owned one but believe me, for every good review there seems to be countless others that slate it. It seems to struggle in anything more than a breeze & the mechanism would seem to prone to faults. There are far superior bivvies on the market at around the same budget, that are as quick to put up including the Fox Evo, Pioneer Ultralight, JRC STI Brolly (not really a brolly), JRC Defender Brolly (not really a brolly) ... all of these are in a different league. To suggest changing from a Chub Cyfish (superb bivvy) for the TFG would be a big step backwards imo
Day Shelters.
What do you want a day shelter for ?? .... Is it literally for days, a few hours on the water, or roaming the river, or trying to fit in those tight little swims that arent suitable for a full size bivvy ??
Anything bigger than a 45"or50" type Nubrolli/Umbrella really for this situations is overkill for days only.
The best alternative option currently on the market & what i use for days is the Korum Day Shelter. It offers far better stability than a brolly, easy to put up, at 3.5kg is lighter in weight than a brolly (oval type), is waterproof and has plenty of room for chair & gear whilst having a sensibly sized footprint. Highly recommend it