The line in the link is a long midbelly speyline. Would be rough with a 10' 8wt.
If you want a floating longish belly single hand line for speycasting try this one.
http://royalwulff.com/products/triangle-taper-floating-fly-line/

 

Grain weight

well that would explain a lot, does anyone happen to know the grain weights for the Salmon/Spey lines? I found a thread listing the specs for the multi tip lines but still looking for this particular line

 

I still stock these lines...

ROYAL WULFF TRIANGLE TAPER SPEY LINES

FLOATING-70' HEAD---7, 8, 9, 10--FLOATING-80' HEAD---10, 11, 12
-------------------------------------------------------------------------------
TRIANGLE TAPER FLOATING SPEY LINE SPECS
ALL LINES ARE 120' OVERALL
-------------------------------------------------------------------------------
LINE WEIGHT/70'
SIZE GRAMS
TT-7-F---27.00 +- 1.50
TT-8-F---32 .00+- 1.50
TT-9-F---36.6 0+- 1.50
TT-10-F---41.00 +- 1.50
TT-11-F---50.75 +- 2.00
TT-12-F---59.25 +- 2.00
NOTE: The 7 and 8 wt. lines have 65' heads but are weighed at 70'
NOTE: The 11 and 12 wt. lines have 80' and 75' heads respectively
NOTE: 1 GRAM=15.432 GRAINS

 

Sweet

See this is why I dig this forum, because there are guys that have the knowledge/resources to further another lesser body like myself. this site kicks butt!

 

I've used the Wulff triangle taper on my 10" 7wt for a few years and I love it for SH spey casting. I overlined it to 8wt and cut about 4 ft off. It is really an effortless line to cast, within reason. No giant flies and tips, but it'll cast a reasonable poly and a big bugger. I like it because there is minimal stripping for casting. It is hands down my favorite SH line, does everything I want it to.