What Bigtoe and T20 will aim to do, on most examples, is not to reduce, but to increase the TP diameter. What they aim to reduce is the LENGTH of the TP, raising the static comp ratio, thus increasing efficiency.
If you look at the most efficient guns on the market, they have short transfer ports, like the HW77/97, HW80, Diana 52 variants and I'd guess the Air Arms TX and Prosport and the HW95.
The HW35, as much as I love them.....I had three until this morning, now four, is an old design and not as efficient. Lovely, lovely rifle with lots of character and charm, accurate and powerful and able to do the business today, but it isn't as efficient as some of these later models.
Until you look at Mick's HW35/LGV 25mm conversion with the short transfer port.