In the real world, the adaptations that allow spiders to walk upside down would be insufficient to support the weight of a giant spider.
Spiders walk upside down by the use of tiny, sticky hairs on their legs.
In case you’re dreaming of someday climbing walls, Wolff added that it’s unlikely we’ll have any real-life Spider-Mans anytime soon: Even if we donned a suit of sticky hairs, people are simply too heavy for it to work.
- National Geographic
Since a normal size adult human weighs about as much (ideally and very roughly between 100-200 lbs) as your giant spiders (132-154 lbs), it seems that the giant spiders couldn't walk upside down either.
Someone who is good with mathematics might be able to interpret the following paragraph from the study cited above and determine just how much weight can be born by spider leg adhesive:
For all eight legs in contact, an average force of 97 mN was measured, which is three times higher than the average spider body weight. With the decreased number of intact legs, attachment force decreased more rapidly than would be predicted due only to the loss of available adhesive pad area (Fig. 1). If the adhesive surface of the first pair of legs was disabled, the mean force was reduced to 74% of its original value (77% predicted). Interestingly, when the fourth pair of legs did not attach to the substrate, the mean force was reduced to 27% (71% predicted). For two pairs of legs with disabled adhesive surfaces, the attachment forces were reduced to 27% of their original value for disabled front legs (53% predicted) and 9% for disabled hindlegs (47% predicted). With only the first leg pair remaining intact, initial forces dropped to 2% (23% predicted) and for the last pair of legs remaining intact they dropped to 6% (28% predicted) of the attachment force obtained with untreated animals.
The good news is that we're having more luck with studying the adhesive properties of gecko feet.