John,
you are correct on the weight but bear in mind how heavy the 12 cylinder engine is....the 6 cylinder flat six is considerably lighter...so its almost a wash...
The 917 still uses a version of radius rod suspension but the forward link locations do not continue through to the bulkhead as per Lola and Gt40.
The mono version uses the same geometry as our "original" tube car which is based on the 69/70 season car....
Hope this helps....