The Nov. 1977 pages 425-432 issue of S&T has the article on the Dillworth scope which is a brother to the Sigler telescope. You may find the Sigler a bit easier to check out as it uses a planoconcave mangin mirror (second surface mirror) and thus you will be able to use a standard negative lens to do some testing. Both designs have the focal plane inside the scope and relay lenses are used to bring the focal point outside of the scope. Neither scope has gotten much in the way of a following, probably due to the mangin mirror which is kind of a strangeness for the average amateur that wants an all reflective telescope if possible and then there's the lenses that are used to move the image outside of the telescope. At F1.5 the design will be quite short as the mangin mirror is not beyond the focus point of the primary. You might want to grab a raytracing program and figure out what the exact numbers are going to be. The positions of the elements will be rather exact to get the capabilities out of the scope but if you're a decent machinist then that will be no problem. Good luck finding the issue of the magazine. The Sigler telescope was in an article in Telescope Making Magazine (rather hard to find if you don't have a real TN in your club) issue #2 Winter 1978.